JP2016221680A - Drive mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exoskeletal robot with a hybrid electro-pneumatic actuator capable of achieving accurate controllability, while reducing weight of the exoskeletal robot.SOLUTION: Each active joint constituting an exoskeletal robot 1 includes a hybrid electro-pneumatic actuator. The hybrid electro-pneumatic actuator includes a pneumatic air muscle and wire for transmitting driving force of the air muscle to the joint. According to a command from an external control device 20, a control part 134 controls pressure to be applied to the air muscle for generating the driving force by an inverse model as a combination of a dynamic model using the wire as a spring represented by a prescribed spring constant, and a driving force model representing prescribed relationship of the driving force to a contraction rate of the air muscle.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a power assist robot that supports a user's exercise.

  In recent years, research on a brain machine interface (BMI) that controls external robot devices using brain information for the purpose of motion reconstruction has attracted attention (Non-Patent Document 1). On the other hand, robots that can balance and walk have been developed. For example, there is a robot that can optimally distribute an action force necessary for movement to a plurality of contact points in space and generate torque of each joint in the same way as a human (see Patent Document 1).

  Several exoskeleton-type robots have been developed with the aim of supporting lower limb and trunk movements.

  The aging society with a declining birthrate caused by the declining birthrate is increasingly demanding the development of robots that support rehabilitation such as exoskeleton robots. For example, exoskeleton type robots are used for patients with spinal cord injury in rehabilitation that promotes the patient's independent life (see, for example, Non-Patent Documents 2, 3, 4, 5, and 6).

  Among these exoskeleton-type robots, the type that supports the weight uses a large electric motor or hydraulic cylinder, and the weight of the robot body is considerably large. On the other hand, as a rehabilitation application that does not support weight, there is one that uses pneumatic artificial muscle (hereinafter referred to as “air muscle”).

  Air muscles are lighter and cheaper to manufacture than other actuators, and have a unique air pressure softness. On the other hand, it has been said that it is not suitable for precise control because of delay, nonlinearity, and individual variation.

  In order to deal with such a problem of air muscle, an air-hybrid hybrid actuator in which a pneumatic air muscle and an electric motor are combined has been proposed (see Patent Document 2).

  More generally, a robot called a “power assist robot” is designed to reduce the burden on the operator by causing the actuator to generate a driving force based on the operating force when the operator tries to move the object. It is a robot. Mainly used in industrial fields such as assembly in factories as well as welfare fields such as nursing and rehabilitation.

  The power assist robot can be divided into a wearing type and a non-wearing type. Exoskeleton type robots as described above are classified as wearing types, while non-wearing type robots such as robot arms, actuators that drive the frame structure, motors, springs, pneumatic cylinders, hydraulic cylinders, air muscles, etc. Those that use are known.

WO2007 / 139135 Publication JP 2012-045194 A

Lebedev, M.A. and Nicolelis, M.A .: “Brain-machine interfaces past, present and future”, Trends in Neuroscience, vol. 29, no. 9, pp. 536-546, 2006. K. Suzuki, M. G. Kawamoto, H. Hasegarwa, and Y. Sankai. Intension-based walking support for paraplegia patients with Robot Suit HAL. Advanced Robotics, Vol. 21, No. 12, pp. 1441-1469, 2007. S. K. Au, P. Dilworth, and H. Herr. An ankle-foot emulation system for the study of human walking biomechanics.In IEEE International Conference on Robotics and Automation, pp. 2939-2945, 2006. H. Kobayashi, A. Takamitsu, and T. Hashimoto. Muscle Suit Development and Factory Application. International Journal of Automation Technology, Vol. 3, No. 6, pp. 709-715, 2009. G. Yamamoto and S. Toyama.Development of Wearable Agri-Robot- Mechanism for Agricultural Work. In IEEE / RSJ International Conference on Intelligent Robots and System, pp. 5801-5806, 2009. T. Kagawa and Y. Uno.Gait pattern generation for a power-assist device of paraplegic gait.In The 18th IEEE International Symposium on Robot and Human Interactive Communication, pp. 633-638, 2009.

  The pneumatic hybrid actuator uses a drive mechanism driven by two different energy sources as a complementary actuator, and enables flexible torque control having elasticity. One drive mechanism is a pneumatic actuator using a pneumatic air muscle, which is suitable for weight reduction. However, as described above, the compressibility of the pneumatic actuator is difficult to control because it is slow in response and causes nonlinear dynamics.

  On the other hand, the electric actuator, which is another driving mechanism, has a characteristic that it is easy to control quickly. However, when an electric actuator using an electric motor tries to control a large torque, the actuator heats up or increases in weight. For this reason, even in the pneumatic hybrid actuator, increasing the size of the electric actuator is contrary to the weight reduction.

  Here, in the non-wearing type power assist robot as well, especially in the case of an exoskeleton type robot for the purpose of rehabilitation as described above, weight reduction is an important issue, so the pneumatic type that is the driving force source Of course, it is necessary to reduce the weight of the air muscle and the electric motor, but it is also important to reduce the weight of the transmission mechanism for transmitting the force from these driving force sources to the joint part of the exoskeleton robot.

  However, reducing the weight of the transmission mechanism may further complicate the dynamics of the control target and increase the difficulty of control.

  The present invention has been made to solve the above-described problems, and is a power assist capable of achieving accurate controllability while reducing the weight of a power assist robot including an aerodynamic hybrid actuator. Is to provide a robot.

  According to one aspect of the present invention, a power assist robot includes a frame structure, an active joint arranged to make the frame structure movable, and a control unit that operates the active joint by torque control on the active joint. Each active joint includes an air muscle, an electric motor, and a drive for driving the bending and extension of the active joint by combining the first driving force from the air muscle and the second driving force from the electric motor. A force synthesis unit and a wire for transmitting the first driving force from the air muscle to the driving force synthesis unit, and the control unit includes a dynamic model and an air model in which the wire is a spring represented by a predetermined spring constant. The pressure applied to the air muscle to generate the first driving force is controlled by an inverse model in combination with the driving force model that represents a predetermined relationship of the first driving force to the contraction ratio of the muscle. That.

  Preferably, a first sensor for detecting a joint angle of each active joint is further provided, and the control unit detects a contraction ratio of the air muscle based on a detection result of the first sensor.

  Preferably, each air muscle further includes a second sensor provided at a joint between the air muscle and the wire for detecting the magnitude of the first driving force from the air muscle. The first driving force of the air muscle and the second driving force from the electric motor are controlled according to the detection result of the second sensor.

  Preferably, the power assist robot is an exoskeleton type robot for supporting a target human musculoskeletal motion, the frame structure corresponds to the exoskeleton, and the active joint is in the musculoskeletal motion. The frame structure is arranged so as to be movable corresponding to each position of the target human joint.

  Preferably, the air muscle includes a fluid bag and a spiral fiber in which the fluid bag is embedded, and when the compressed air is fed and the fluid bag expands, the air muscle contracts in the longitudinal direction. Is a function of the shrinkage ratio, the diameter of the air muscle at normal pressure, and the angle of inclination of the winding direction with respect to the shrinking direction of the spiral fiber.

  Preferably, the wire is made of liquid crystal polymer fiber.

  According to the present invention, it is possible to provide a power assist robot that combines an air muscle and an electric motor, reduces the weight of a driving force transmission mechanism, and can accurately control a high load torque necessary for assisting human movement.

It is a figure which shows the structural example of the exoskeleton type robot 1 in this Embodiment. It is a figure which shows the structure of the freedom degree of the exoskeleton type robot. 2 is an example of a block diagram of the exoskeleton robot 1. FIG. It is a figure which shows the external appearance which extracted the part of the aerodynamic hybrid actuator which performs operation | movement for 1 degree of freedom in the structure of an exoskeleton type robot. It is a functional block diagram for demonstrating the structure which controls the system of the pneumatic hybrid actuator which performs operation | movement for 1 degree of freedom. It is a conceptual diagram for demonstrating the aspect which each actuator moves a joint. It is a figure which shows the state of each joint of an exoskeleton type robot in a crouched posture and an upright posture, and a pneumatic air muscle. It is a figure which compares and shows the operating range of the contraction ratio of a pneumatic air muscle, and a driving force. It is a figure which shows the response characteristic of the torque controller observed using a 1 degree-of-freedom system. It is a figure which shows the gravity correction | amendment task in the state by which the weight was suspended by the edge part of the end effector of the arm of 1 degree of freedom of an electrostatic hybrid actuator. It is a figure which shows the operation | movement which supports the standing task achieved by the gravity correction which an exoskeleton type robot switches two different movement models.

  Hereinafter, the configuration of the exoskeleton robot according to the embodiment of the present invention will be described with reference to the drawings. In the following embodiments, components and processing steps given the same reference numerals are the same or equivalent, and the description thereof will not be repeated unless necessary.

  Hereinafter, in the present embodiment, an aerodynamic hybrid exoskeleton robot for walking / posture rehabilitation will be described.

  However, the aerodynamic hybrid exoskeleton robot of the present invention can be used not only as an exoskeleton robot for assisting the movement of the lower limbs but also as an exoskeleton robot for assisting the movement of the upper limbs. Is possible.

  Further, in the following description, an exoskeleton type robot that assists exercise as a pair of lower limbs will be described. However, an exoskeleton type that assists exercise of either one of lower limbs or upper limbs. It can also be used as a robot.

  Furthermore, if the aerodynamic hybrid exoskeleton robot of the present invention assists the movement of the target human musculoskeletal system, the above-described “at least one of the lower limbs or the upper limbs” It is not limited to “at least one of these exercises”. For example, it may assist only the exercise of the subject's lower back, or it may be linked with the exercise of the lower limbs during walking or running. And assisting the exercise of the lower back. In the present specification, such assist of human motion as a target is generically referred to as “support of target human musculoskeletal motion”.

  Further, the aerodynamic hybrid drive mechanism of the present invention is applied not only to an exoskeleton type robot but also to a more general power assist technology, and assists the work of an operator who handles heavy objects. Can also be realized. However, in the following, as an embodiment of the present invention, an “exoskeleton robot” will be described as an example.

  The exoskeleton type robot of the present embodiment has an exoskeleton. “Exoskeleton” refers to a skeleton structure that a robot has corresponding to a human skeleton structure. More specifically, “exoskeleton” refers to a frame (framework) structure that supports a part of a human body to which an exoskeleton-type robot is mounted from the outside.

  The frame structure is further provided with a joint for moving each part of the frame structure in accordance with the movement based on the human skeleton structure.

  In particular, an exoskeleton-type robot that assists the movement of the lower limbs is a robot having a base and a lower half body, and having joints with 6 degrees of freedom in the left and right positions of the ankle, knee, and waist. Further, the six joints are aerodynamic hybrid drive joints. Hereinafter, in the exoskeleton robot, the joint driven by the actuator is referred to as an “active joint”.

  FIG. 1 is a diagram showing a configuration example of an exoskeleton robot 1 in the present embodiment. The exoskeleton robot 1 has 10 degrees of freedom.

  In FIG. 1, FIG. 1 (a) is a diagram showing the appearance of an exoskeleton robot, and FIG. 1 (b) is a diagram showing the main part of the exoskeleton robot 1 extracted from the appearance of FIG. 1 (a). FIG.

  In FIG. 1B, the exoskeleton robot 1 has a frame structure corresponding to both legs, a backpack 101, a flexible sheet 102, a HAA antagonist muscle 103, an HFE extensor muscle 104, an HFE motor 111, a KFE extensor muscle 105, and a KFE motor. 106, an AFE extensor 107, an AFE flexor 108, a joint 109, and a rotary joint 110 with a pulley provided in the frame structure.

  In FIG. 1B, the backpack 101 is directly attached to the structure for supporting exercise. However, as shown in FIG. 1A, the backpack 101 may be removed from this structure. .

  Further, for example, an optical encoder is attached to the rotary shaft of the rotary joint 110 with pulley, and the joint angle is measured. The optical encoder may not be attached to the shaft, but may be configured to read the moving direction and the moving amount of the belt wound around the shaft. Note that in the HFE and KFE joints which are hybrid joints, the joint angle may be measured using an encoder attached to the motor. The joint 109 corresponds to an AAA joint, and in this configuration, a drive mechanism is not attached and the joint 109 is a passive joint.

  FIG. 2 is a diagram illustrating a configuration of the degree of freedom of the exoskeleton robot 1.

  In FIG. 2, in each joint, the display “R_” indicates the right joint, and the display “L_” indicates the left joint.

  Referring to FIGS. 1 and 2, the HFE joint and the KFE joint out of all 10 degrees of freedom are hybrid drives. In FIG. 2, out of all 10 degrees of freedom, the left and right AFE joints employ antagonistic drive using extensors and flexors. The joints other than the hybrid drive and the antagonist drive are passive drives. However, more joints, for example, all joints may be hybrid driven.

  In FIG. 1, a posture sensor is mounted on the body portion to which both legs are connected to detect the posture of the base portion. In addition, wire type encoders (or encoders attached to motors) are attached to all joints so that joint angles can be measured. By detecting the posture and joint angle of the base, an accurate Jacobian matrix from the center of gravity to the contact portion can be calculated, and the target torque to be generated at each joint can be calculated.

  In addition, a floor reaction force sensor is mounted on the sole, and it is used as an auxiliary to determine whether the sole that is supposed to touch is actually touching or to correct the model error included in the Jacobian matrix It is good also as composition to do.

  A method for calculating a torque value to be allocated to each actuator from a target acting force based on a forward kinematic model using such a Jacobian matrix is disclosed in, for example, Patent Document 1 described above.

  In addition to the controller, the backpack 101 incorporates an air muscle valve and an electric motor driver.

Further, a backpack 101, a battery and compressed the CO ₂ gas cylinder, equipped with a regulator, in case the power supply line and the air supply is disconnected, may be configured to allow a short time autonomous driving.

  FIG. 3 is an example of a block diagram of the exoskeleton robot 1.

  A command for controlling the exoskeleton robot 1 is given from the external control device 20 to the exoskeleton robot via a communication path. Although not particularly limited, the external control device 20 can use a general-purpose personal computer, and an Ethernet (registered trademark) cable can be used as a communication path. Of course, as a communication path, a wireless communication path such as a wireless LAN (Local Area Network) or another communication standard may be used in addition to a wired communication path of another standard.

  The external control device 20 includes an input unit 210 that receives an instruction input from a user, a nonvolatile storage device in which data necessary for control such as a program for generating a command and various control parameters is recorded. 206, a memory 204 including a ROM (Read Only Memory) in which firmware for starting the external control device 20 is stored, a RAM (Random Access Memory) that operates as a working memory, and the like. Under the control of the computing device 208, the computing device 208 that executes the processing to generate, the interface (I / F) unit 202 for transmitting commands to the exoskeleton-type robot via the communication path, and the computing device 208 And a display device 212 for displaying information on the state of control of the robot 1.

  As described above, when the external control device 20 is a general-purpose personal computer, the arithmetic device 208 is configured by a CPU (Central Processing Unit), and the nonvolatile storage device 206 includes a hard disk drive, a solid state drive, and the like. Can be used. However, some or all of the functional blocks of the external control device 20 may be configured by dedicated hardware.

  Further, the external control device 20 may be a device that detects brain information of a user to which the exoskeleton-type robot is attached and generates a command for controlling the exoskeleton-type robot. In this case, the exoskeleton robot is controlled by a so-called brain machine interface.

  The exoskeleton robot 1 includes an exoskeleton part 12 and an internal control device 10.

  The exoskeleton 12 includes a base 121, a lower body 122, an active joint 123, and a detection mechanism 124. Further, the active joint 123 includes an air muscle 1231 (not shown) and an electric motor 1232 (not shown).

  The internal control device 10 also includes an I / F unit 11, a recording device 131, a storage device 132, a measuring device 133, a control unit 134, and an output device 135.

  The I / F unit 11 can receive a torque or a position command that is commanded from the external control storage 20 or decoded from the brain information. Here, the brain information defines, for example, information indicating that the right leg is raised, information indicating walking and walking speed, and the movement of the trunk and lower limbs including the torque value of a specific joint. Information.

  The base 121 may be considered to include the skeleton at the waist position and the active joint 123 at the waist position, or may be considered to be only the skeleton at the waist position.

  The lower body 122 may be considered to include the skeleton at the position of the thigh or foot, the active joint 123 at the position of the thigh or foot, or may be considered to be only the skeleton at the position of the thigh or foot.

  The active joints 123 are active joints arranged at left and right ankles, left and right knees, and left and right positions of the waist. Here, the active joint 123 is a joint that can be actively operated by an actuator. That is, the active joint 123 includes an actuator.

  Further, the one or more active joints 123 here are of a hybrid type. That is, at least a part of the active joint 123 is a hybrid type including the air muscle 1231 and the electric motor 1232. The actuator has a function of receiving a torque value as a control target value as a drive signal and controlling based on the received torque value.

  When a servo motor is used as an actuator, the actuator has, for example, a drive circuit capable of current control, and a servo motor that generates a torque proportional to the current has a gear value that is input as a control target value. Torque control for generating the input torque is realized by instructing the drive circuit by multiplying the torque constant determined by the ratio. In particular, by providing a torque sensor at the active joint 123 and feeding back a value detected by the torque sensor to the drive circuit, highly accurate torque control is possible.

  The detection mechanism 124 detects the state of the robot. The detection mechanism 124 includes, for example, an encoder disposed at each joint, a floor reaction force sensor disposed at the foot, a gyro sensor for posture detection disposed at the pelvis, and a load cell that detects the driving force of each air muscle. Etc. The detection mechanism 124 may be an angle sensor that detects the angle of the joint, a posture sensor that acquires the posture of the robot, an external force sensor, or the like.

  The internal control device 10 operates the active joint 123. The internal control device 10 operates the active joint 123 in response to the torque or position command received by the I / F unit 11. For example, the internal control device 10 converts the target floor acting force into the respective torque values of the respective actuators that drive each active joint 123 based on the forward kinematic model defined by the Jacobian matrix. The converted torque values are output to the actuators as control target values.

  The measuring device 133 receives various signals (data) indicating detection results from the detection mechanism 124 such as a sensor.

  The control unit 134 performs various calculations such as calculation of a control target value. The calculation performed by the control unit 134 will be described later.

  The output device 135 outputs a control signal to the active joint 123. For example, the output device 135 outputs a target torque value to the active joint 123.

(Torque controller for pneumatic hybrid actuator)
Below, the structure of the torque controller for an aerodynamic hybrid actuator is demonstrated.

  As will be described below, such a controller can be configured to be executed by causing the control unit 134 to execute machine learning.

  The pneumatic air muscle is lightweight, and can generate a large force by converting the energy of compressed air (or compressed gas) into a contracting force by a rubber tube.

  The principle that an air muscle generates force is that a spiral fiber embedded with a pneumatic air bag shrinks in the longitudinal direction (longitudinal direction) when compressed air is fed and the air bag expands. is there.

  More specifically, the rubber tube with plugs at both ends is covered with a spirally wound fiber on the surface so as to restrain the radial direction. When air is fed into the rubber tube, the rubber tube expands due to the pressure of the air. However, since the radial direction is constrained by the fiber, it cannot expand, and is pulled by the radial expansion and contracts in the vertical direction. The place that resembles an animal's muscles that swell and contract is called an artificial muscle.

  The actuator itself is light and soft. Furthermore, since the entire inner surface of the rubber tube contributes to the contraction of the actuator, the power / weight ratio can be made larger than that of a general air cylinder or the like having a structure that receives pressure only by a cross-sectional area. On the other hand, as described above, in general, device control by air pressure has a large control delay due to air contraction / expansion and is not good at quick operation.

  As long as the “air bag” is inflated or contracted by a fluid, what flows into the bag is not limited to air, and is more generally expressed as a “fluid bag”.

  FIG. 4 is a diagram showing an external appearance of a portion of an aerodynamic hybrid actuator that performs an operation for one degree of freedom in the configuration of an exoskeleton type robot.

  In FIG. 4, the upper air muscle 302 of the pneumatic air muscles corresponds to the flexor (PAM1), and the lower air muscle 304 corresponds to the extensors (PAM2).

  The extensor PAM2 generates a force opposite to the flexor PAM1.

  Driving force from the electric motor is also applied to the rotary joint 310 with pulley, and the driving force from the pneumatic air muscle and the driving force from the electric motor are combined.

  The driving force from the air muscle 302 is transmitted to the rotary joint 310 with pulley by the wire 306, and the driving force from the air muscle 304 is transmitted to the rotary joint 310 with pulley through the wire 308. With such a configuration, it is possible to reduce the weight of the driving force transmission mechanism itself.

  The leg (or arm) 350 is driven by the driving torque applied to the rotary joint 310 with pulley.

  FIG. 5 is a functional block diagram for explaining a configuration for controlling the system of the aerodynamic hybrid actuator that performs the operation for one degree of freedom shown in FIG.

  In FIG. 5, the internal control device 10 is configured as a multi function board.

  The multifunction board 10 connected to the external control device 20 controls the actuator in accordance with a command from the external control device 20. Specifically, the multifunction board 10 controls the valve 301 and the valve 302 for controlling the contraction of the pneumatic air muscles 302 and 304, and the motor driver 311 for controlling the electric motor 312. Furthermore, the multifunction board 10 reads the measurement data from the angle encoder 324 that detects the joint angle θ, the load cell that detects the driving force from the air muscle, and the torque sensor that detects the torque applied to the active joint. Based on this, control as described below is executed.

  As the angle encoder 324, for example, a quadrature encoder can be used.

  The driving forces from the air muscles 302 and 304 and the electric motor 312 are combined at the rotary joint 310 with a pulley and give a torque τ to the leg 350.

  FIG. 6 is a conceptual diagram for explaining a mode in which each actuator moves a joint.

  In the following, first, let us consider a case where the extension of the tendon wire can be ignored as shown in FIG.

The driving force f _PAMi (i = 1, 2,...) From the pneumatic air muscle force is transferred / converted as torque to the arm (or leg) by the wire and the pulley. The driving force of the electric motor is also transmitted through this pulley. The driving force f _PAMi from the pneumatic air muscle force is detected by a load cell provided at the junction between the pneumatic air muscle and the wire that transmits the driving force to the pulley.

  The description of the following model is not limited to the combination of the antagonistic muscle and the electric motor, but can be widely applied to the combination of the extensor and the electric motor, for example. However, in the following, for simplicity of explanation, a simple two antagonistic muscle model is considered.

The torque τ _PAM is _expressed by the following formula _using the driving force f _PAMi .

τ _PAM is the torque due to the driving force of the pneumatic air muscle, while r ₀ is the pulley radius, and in this simple model, r ₀ is a constant.

  Torque due to the driving force of the motor is transmitted in parallel with the driving force of the pneumatic air muscle. For example, a small torque is transmitted via a pulley by a mechanical belt.

The pneumatic air muscle is excellent in generating direct current or low frequency torque. In addition, since the driving force by the electric motor is a quick and high frequency torque and covers the error of the torque τ _PAM due to the driving force of the pneumatic air muscle, the value of the electric torque τmotor is the torque by the pneumatic air muscle. A smaller value is acceptable.

  The total torque is expressed by the following formula.

τ = τ _PAM + τmotor
Therefore, although not particularly limited, for example, the internal control device 10 causes the electric motor 312 to additionally operate with respect to torque that is at a higher frequency than the first threshold (assuming that “more” includes “more”). Is preferred. The additional operation is to operate the electric motor 312 in addition to the air muscles 302 and 304. Here, the first threshold is, for example, 3 Hz.

  From the pneumatic air muscle, the wire transmits the driving force to the pulley and drives the joint in one designated direction.

  As the wire, a liquid crystal polymer fiber can be adopted because it is lighter, stronger and more flexible than a metal wire, chain, or mechanical belt. As the liquid crystal polymer fiber, for example, Vectran (registered trademark) manufactured by Kuraray Co., Ltd. can be used, which is known as a material having high strength and high elastic modulus even though it is a polymer fiber.

(Mechanical model of pneumatic air muscle)
Pneumatic actuators, including pneumatic air muscles, wires and pulleys, have much in common with human muscles.

  When an exoskeleton robot supports the weight of a human, the wire resembles a human tendon in its characteristics.

  Therefore, as described below, a torque controller for a pneumatic air muscle is derived with the assumption of equilibrium.

  For controlling the pressure of the pneumatic air muscle, for example, a valve that adjusts the pressure proportionally is used, and the pressure p is controlled by a closed feedback loop and is sufficiently stable.

  In the transient state, there is an aerodynamic movement between the valve pressure and the pressure of the pneumatic air muscle, but after a certain time constant, there is an external movement such as the weight of the robot and human. The pneumatic air muscle contracts until the driving force is balanced with the above constraints.

  Therefore, the influence of air circuit dynamics is small and can be ignored in quasi-static operation.

  At this equilibrium point, the driving force generation depends on the internal pressure and contraction rate, and the driving model of the pneumatic air muscle is given as follows:

Here, ε is a contraction ratio, and D ₀ and ψ ₀ are the diameter of the pneumatic air muscle at normal pressure, and the spiral fiber in which a pneumatic air bag is embedded in the pneumatic air muscle. It is the angle of inclination of the winding direction with respect to the direction orthogonal to the shrinking direction.

  Such a “pneumatic air muscle driving force model” is disclosed in the following document, for example.

Reference 1: K. Inoue. Rubbertuators and applications for robots. In Proceedings of the 4th international symposium on Robotics Research, pp. 57-63. MIT Press, 1988.
Reference 2: DG Caldwell, A. Razak, and MJ Goodwin. Braided pneumatic muscle actuators. In Proceedings of the IFAC Conference on Intelligent Autonomous Vehicles, pp. 507-512, 1993.
Unlike air cylinders, torque changes nonlinearly as joint angles change.
Under the assumption that the motion constraints are always unchanged, the pressure of the pneumatic air muscle will always give the contraction rate ε (p) at the same equilibrium point. That is, the shrinkage ratio ε (p) is a function of the pressure p.

  At this time, an inverse model of the “pneumatic air muscle driving force model” can be learned by machine learning. That is, it corresponds to obtaining the pressure p for obtaining a desired driving force f. The internal control device 10 outputs a desired driving force by controlling the valve so as to apply such a pressure p to the air muscle.

  For example, Hartman et al. Have proposed dynamic learning in the following literature.

Reference 3: Christoph Hartmann, Joschka Boedecker, Oliver Obst, Shuhei Ikemoto, and Minoru Asada. Real-time inverse dynamics learning for musculoskeletal robots based on echo state gaussian process regression. In Accepted at RSS 2012, 2012.
However, in general, since the constraints on motion are dynamically changed and balanced with different external forces F, this assumption does not hold strictly in an exoskeleton robot as described above.

  Therefore, the contraction ratio ε at the equilibrium point in this case is expressed as ε (p, F) as a function of pressure and external force.

(Tendon spring equilibrium model)
Since the wire made of the liquid crystal polymer fiber as described above has a high strength and a high elastic modulus, the approximation that the length does not change with respect to the tension usually holds well. Examples of the high-strength / high-modulus fiber include ultra high molecular weight polyethylene fiber and PBO fiber in addition to polyarylate fiber such as Vectran (registered trademark).

  However, to hold a human (eg, weigh 60 kg), a pneumatic air muscle typically produces 3000 N as a tension (for example, a maximum of 5000 N is required). .

  When such a large force is applied, even if it is a wire (tendon wire) made of a liquid crystal polymer fiber, the extension amount cannot be ignored and the equilibrium point is changed.

  Below, as shown in FIG.6 (b), the model which considered the influence of the expansion | extension of a tendon wire is examined.

  Therefore, a linear tendon spring model as described below is introduced as a mechanical model of a tendon made of liquid crystal polymer fiber.

f = kΔε (2)
That is, in this model, the tendon wire (wire made of liquid crystal polymer fiber such as polyarylate fiber) is approximated to a spring, Δε is the extra air muscle contraction caused by the force, and k is the spring constant. is there. In other words, the pneumatic air muscle needs to be contracted excessively as much as the tendon extends by force. Such a tendon wire approximated to a spring will be referred to as a “tendon spring”.

  When the wire corresponding to such a tendon is not approximated as a tendon spring, the pneumatic air muscle driving force model g () has three parameters (two of which are dependent): Represented by equation (3):

here,
The following relationship holds for the coefficients of the quadratic expression.

At the equilibrium point, the driving force f ^* decreases as follows due to the extension of the tendon.

Where g ′ () is the driving force model under the assumption of tendon spring, ε ^* is the apparent contraction rate, ε is the actual contraction rate of the pneumatic air muscle, and Δε is This is an additional term to the actual contraction ratio of the pneumatic air muscle.

From equation (2), Δε = f ^* / k.

It is difficult to directly measure the actual contraction ratio ε with the detection mechanism 124 of the exoskeleton robot as described above. Therefore, the estimated shrinkage ratio εest (= ε ^* + Δε) is used instead. The contraction ratio ε ^* is calculated from the joint angle as in the following equation.

Here, L ₀ is the initial length of the pneumatic air muscle when the joint angle θ = 0. In other words, the “apparent contraction ratio” is a contraction ratio derived from a change in the angle of the joint driven by the actuator, and is based on an amount that can be detected by the angle sensor, whereas “actual contraction ratio”. The “ratio” is the rate at which the air muscle is actually contracted to generate the driving force f ^* .

When the driving force f ^* is required at the contraction ratio ε ^* , the necessary pressure p ^* is derived from the inverse model g ⁻¹ () as follows.

Pneumatic air muscle parameters a, b and c can be estimated from known pneumatic air muscle data using a least squares algorithm.

  Furthermore, for example, when the equilibrium point driving force is measured by a one-degree-of-freedom system in a calibration experiment, an optimum value can be experimentally obtained by manually adjusting the spring constant k.

The main torque that assists the motion (torque of a component below a predetermined frequency, for example, DC component torque) is supplied by a pneumatic air muscle, and the actual torque τ _PAMs can be measured by a load cell. As described above, high-frequency torque (component torque exceeding a predetermined frequency: torque of AC component) is generated by the electric motor.

  Therefore, the torque of the motor is expressed as the following equation (7).

As described above, by applying the tendon spring model to the tendon wire, in the configuration for detecting the joint angle and the driving force applied to the tendon wire, the inverse model that correctly reflects the driving force of the pneumatic air muscle is For example, it can be constructed by machine learning. As a result, when controlling the aeroelectric actuator, it is possible to improve the frequency response as described below.
(Generation of vertical force to support standing motion)
Hereinafter, a configuration for supporting vertical motion, for example, standing motion by the exoskeleton type robot will be described.

  The force (assist force) of the exoskeleton robot that supports the vertical movement is generated as follows.

Here, J is a Jacobian matrix that associates the assist force by the robot and the torque to each joint of the exoskeleton robot, and F is a virtual force F that supports the standing motion.

  Here, only the force in the vertical direction is considered, and the force in the horizontal direction is considered to be generated by the motion of the user's upper body.

  FIG. 7 is a diagram showing the state of each joint of the exoskeleton robot and the pneumatic air muscle in a crouched posture (FIG. 7A) and an upright posture (FIG. 7B).

  As shown in FIG. 7 (a), the pneumatic actuator generates a large tension in a lower crouching posture.

  As shown in FIG. 7B, in the upright posture, the torque required for balancing and maintaining the posture is small.

  FIG. 8 is a diagram comparing the operating range of the contraction ratio and the driving force of the pneumatic air muscle.

  FIG. 8 shows a comparison between a model with a tendon spring model and a pneumatic actuator model without a tendon spring model (PAM original model), and also shows the measurement results of the force generated at each contraction ratio. In the figure, v represents the control voltage of the pressure control valve and has a proportional relationship with the pressure in the air muscle.

  By considering the tendon spring model, it can be seen that the torque controller reproduces the measured driving force well, especially in the large driving force range.

  FIG. 9 is a diagram illustrating the response characteristics of the torque controller observed using the one degree of freedom system.

  In FIG. 9, the desired torque, which is an input as a control target, is a sine wave, and the case where the characteristics of only the pneumatic air muscle are considered and the tendon spring model are compared and shown.

  With the pressure of the air muscle (extension) that generates the reaction force maintained at the maximum value (0.6 Mpa), input a signal to the controller to generate a sinusoidal torque in the flexor air muscle. Yes. The joint is driven by such a signal input.

  FIG. 9 shows that in the tendon spring model, a torque closer to the desired torque can be generated without substantially changing the time delay in the frequency response.

  In addition, in FIG. 9, the time response of the tendon spring model by driving a pneumatic air muscle is compared for the comparison with the conventional air muscle only model (PAM original model) which does not consider a tendon spring. . However, in the case of the air / electric hybrid drive, as described above, the torque and the error due to the desired torque and the driving force of the air muscle are covered by the torque of the electric motor. A desired torque can be obtained.

  FIG. 10 is a diagram showing a gravity correction task in a state where a weight is suspended from the end of the end effector of the arm having one degree of freedom of the static electricity hybrid actuator.

  A pneumatic hybrid actuator having the configuration shown in FIG. 4 is used.

  Each figure is extracted from a moving image as a still image with an afterimage.

  As shown in FIG. 10A, in a state where a 10 kg weight is suspended, a controller using a tendon spring model compensates for gravity so that the arm faces downward.

  Next, as shown in FIG. 10B, even with one finger, the arm can be moved upward.

  Furthermore, as shown in FIG. 10 (c), since the gravity is compensated, the arm stops at an angle facing upward.

  Here, although such a controller is not a position / angle controller but a torque controller, it can move as shown in FIGS. 10 (a) to 10 (c). .

  FIG. 11 is a diagram illustrating an operation for supporting a standing task, which is achieved by gravity correction in which an exoskeleton robot switches two different motion models.

  As shown in FIGS. 11A to 11B, when the sitting state is an initial state, the exoskeleton robot first generates a torque with respect to the robot weight in consideration of only the movement of the robot.

  Next, as shown in FIG. 11 (c), by switching the motion model to one that considers both the robot and the human leg, the human receives the assist force in the upward direction. Is assisted in standing motion.

  As described above, according to the present embodiment, the pneumatic artificial muscle (air muscle) and the electric motor are combined, the driving force transmission mechanism is reduced in weight, and the walking and posture function recovery and assistance are achieved. It is possible to provide an exoskeleton type robot that can accurately control the high load torque required for the operation.

  More specifically, by using the exoskeleton robot of the present embodiment for assisting the movement of the lower limbs, it has the effect of being able to appropriately support the movement of the trunk and lower limbs, and can be used for walking and posture. It is useful as an external bone type robot for rehabilitation.

  In the above description, the exoskeleton robot has been described as an example. However, the present invention is not limited to such a case, and the frame structure (for example, the skeleton structure of the robot arm) and each active joint of the frame structure are described. Any robot can be applied as long as the robot is driven by an electrostatic hybrid. For example, in a work site where heavy objects are frequently transported, the weight of the heavy object is reduced by hanging the heavy object independently of the operator, and the operator can move the heavy object in a desired direction. It can also be applied to power assist robots that enable accurate movement and assembly.

  Embodiment disclosed this time is an illustration of the structure for implementing this invention concretely, Comprising: The technical scope of this invention is not restrict | limited. The technical scope of the present invention is shown not by the description of the embodiment but by the scope of the claims, and includes modifications within the wording and equivalent meanings of the scope of the claims. Is intended.

  DESCRIPTION OF SYMBOLS 1 Exoskeleton type robot, 10 Internal controller, 11 I / F part, 12 Exoskeleton, 20 External controller, 121 Base, 122 Lower body, 123 Active joint, 124 Detection mechanism, 131 Recording processing part, 132 Storage device, 133 Measuring device, 134 control unit, 135 output device, 302, 304 air muscle, 310 rotary joint with pulley, 312 electric motor.

The present invention was made to solve the above problems, while realizing weight reduction, it is to provide a driving mechanism capable of achieving your accurate torque system.

According to one aspect of the present invention , there is provided a driving mechanism for driving an active joint of a robot frame structure, the first sensor for detecting a joint angle of the active joint , and active by torque control on the active joint. A control unit for operating the joint, and the active joint is composed of an air muscle, an electric motor, and a first driving force from the air muscle and a second driving force from the electric motor to bend and stretch the active joint. And a wire for transmitting the first driving force from the air muscle to the driving force synthesizing unit, and the control unit determines the wire when torque controlling the active joint. represented by dynamic models a spring represented by the spring constant of the first driving force, driving by a predetermined function representing the relationship between the contraction ratio of the pressure and the air muscle to be supplied to the air Muscle When expressed as a model, when the first driving force for generating the target torque in the active joint is set as the target driving force, the dynamics are calculated from the apparent contraction ratio calculated from the joint angle detected by the first sensor. Based on the estimated contraction ratio obtained by using the model and the target driving force, the pressure to be supplied to the air muscle is calculated by the inverse model of the driving force model, and the pressure applied to the air muscle is controlled.

Preferably, the predetermined function of the driving force model is the first driving force by the air muscle expressed by a predetermined polynomial between the pressure supplied to the air muscle and the contraction ratio of the air muscle, and the inverse model is It is constructed by machine learning based on the drive model.

Preferably, the control unit calculates an estimated contraction ratio from an apparent contraction ratio using a dynamic model based on the first driving force detected by the second sensor.

Preferably, the air muscle includes a fluid bag and a spiral fiber in which the fluid bag is embedded, and when the compressed air is fed and the fluid bag expands, the air muscle contracts in the longitudinal direction. Is a function of the pressure supplied to the air, the contraction ratio of the air muscle, the diameter of the air muscle at normal pressure, and the angle of inclination of the winding direction with respect to the contraction direction of the spiral fiber.

According to another aspect of the present invention, there is provided a drive mechanism for applying a torque having a frequency component in a predetermined region to a joint of a robot frame structure, an air muscle for generating a drive force corresponding to the torque, and a joint An angle sensor for detecting the joint angle of the wire, a wire for transmitting the driving force from the air muscle to the joint, and a control unit for operating the joint by torque control. The control unit torque-controls the joint In this case, the driving force model is expressed by a predetermined function that expresses the relationship between the pressure to be supplied to the air muscle and the contraction ratio of the air muscle by expressing the wire as a spring expressed by a predetermined spring constant. When the driving force for generating the target torque in the joint is used as the target driving force, the appearance calculated from the joint angle detected by the angle sensor Based from shrinkage percentage upon the estimated shrinkage ratio and the target driving force obtained by using a dynamic model, the inverse model of the driving force model to calculate the pressure to be supplied to the air muscle, controls the pressure applied to the air muscle.

ADVANTAGE OF THE INVENTION According to this invention, the transmission mechanism of the driving force by an actuator can be reduced in weight, and the drive mechanism which can control a high load torque correctly can be provided.

Claims (6)

Frame structure,
An active joint arranged to make the frame structure movable;
A control unit for operating the active joint by torque control on the active joint,
Each active joint is
Air muscle,
An electric motor;
Driving force combining means for driving the bending and extension of the active joint by combining the first driving force from the air muscle and the second driving force from the electric motor;
A wire for transmitting the first driving force from the air muscle to the driving force combining means;
The controller is
An inverse model of a combination of a dynamic model in which the wire is a spring represented by a predetermined spring constant and a driving force model that represents a predetermined relationship of the first driving force with respect to a contraction ratio of the air muscle. A power assist robot that controls a pressure applied to the air muscle to generate a driving force. A first sensor for detecting a joint angle of each active joint;
The controller is
The power assist robot according to claim 1, wherein the contraction ratio of the air muscle is detected based on a detection result of the first sensor. Each of the air muscles further includes a second sensor that is provided at a joint between the air muscle and the wire and detects the magnitude of the first driving force from the air muscle,
The controller is
The power assist robot according to claim 1, wherein the first driving force of the air muscle and the second driving force from the electric motor are controlled according to a detection result of the second sensor. The power assist robot is an exoskeleton type robot for supporting a target human musculoskeletal movement,
The frame structure corresponds to an exoskeleton,
The power assist robot according to claim 2, wherein the active joint is arranged so that the frame structure can be moved corresponding to each position of the target human joint in the musculoskeletal motion. The air muscle is
A fluid bag;
A spiral fiber embedded with the fluid bag,
When compressed air is fed and the fluid bag expands, it contracts in the longitudinal direction,
The driving force model is a function of a contraction ratio of the air muscle, a diameter of the air muscle at normal pressure, and an inclination angle of a winding direction with respect to a contraction direction of the spiral fiber. Power assist robot.   The power assist robot according to claim 1 or 2, wherein the wire is made of liquid crystal polymer fiber.