CN110450159A - The foot condition checkout gear of biped robot a kind of and inclined-plane traveling method based on the device - Google Patents

Abstract

The invention discloses a foot state detection device of a biped robot and a walking method on an inclined plane. The device includes a pressure sensor module, an AD conversion module, an inertia measurement module, a communication module, a microcontroller module and a power supply module. On the basis of realizing the original foot pressure detection function, the foot state detection device can detect the foot angle state, realize the slope information detection of the ground, and provide feedback for the biped robot to walk on the slope. The inclined plane walking method of the invention is simple to implement, and can effectively improve the walking stability and environmental adaptability of the biped robot.

Description

A foot state detection device for a biped robot and an inclined plane based on the device walking method

technical field

The invention relates to the technical field of robot control, in particular to a foot state detection device of a biped robot and an inclined-plane walking method based on the device.

Background technique

Biped robot is a kind of bionic humanoid robot, which can realize upright walking and related actions. Biped robots are expected to help humans solve many problems, such as rescue, emergency rescue, carrying and other dangerous operations or repetitive labor.

If the biped robot is to be applied in various fields, the primary problem is to walk stably, which is also one of the hot spots of biped robot research. At present, most biped robot systems use ZMP (Zero Moment Point) as the criterion for stable walking. Based on this criterion, biped robots can achieve better results when walking on flat ground. The biped robot can install a pressure sensor on the foot, calculate the ZMP position by continuously detecting the pressure sensor data, and then adjust the gait so that the ZMP balance point is inside the polygon to ensure walking balance. What Chinese Patent Nos. CN206114175U and CN202075069U describe is exactly this foot state detection device.

However, in the actual environment, biped robots are likely to encounter various uneven ground such as slopes and steps during walking. Chinese Patent No. CN104331081A proposes a gait planning method for a biped robot to walk on an inclined plane, but the method needs to be configured with information on the angle of the inclined plane and the walking direction. In order to ensure stable walking on the slope, this requires the biped robot to be able to detect the slope angle and walking direction, which puts forward new requirements for the foot detection device of the biped robot.

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides a foot state detection device for a biped robot and a method for walking on a slope based on the device. Provide feedback.

The purpose of the present invention is achieved through the following technical solutions:

A foot state detection device for a biped robot, characterized in that the device includes a pressure sensor module, an AD conversion module, an inertial measurement module, a communication module, a microcontroller module, and a power supply module, and the pressure sensor module includes an arrangement Four pressure sensors around the feet, namely left front S1, right front S2, left rear S3 and right rear S4, are used to sense the pressure between the foot and the ground; the inertial measurement module is arranged in the middle of the sole of the foot position, the X-axis positively points to the front of the sole of the foot, the positive Y-axis points to the left side of the sole of the foot, and the positive Z-axis is vertically upward for measuring the inclination angle of the foot; the pressure sensor module is connected to the AD conversion module , the AD conversion module, the inertial measurement module, and the communication module are all connected to the microcontroller module, and the power supply module supplies power to all other modules; the microcontroller is used to process the pressure information of the sole and tilt angle, and transmit the data to the central controller of the biped robot through the communication module.

Further, the pressure sensor is a pressure sensor that uses resistance strain gauges to form a full-bridge circuit; the AD conversion module uses a 24-bit A/D conversion chip HX711, and the inertial measurement module includes a three-axis gyroscope and a three-axis The axial accelerometer adopts the MPU6050 chip, and is connected to the microcontroller through the I2C interface; the microprocessor adopts the STM32F103C8T6 chip.

A method for walking on an inclined plane of a biped robot, characterized in that the method is implemented based on any one of the above-mentioned foot state monitoring devices, and the method specifically includes the following steps:

Step 1: During the descending process of the swinging leg of the biped robot, adjust the ankle joint to be parallel to the horizontal plane, and detect the data of the four pressure sensors of the swinging leg to judge the footing: when any pressure sensor data > threshold Y is detected, this When the swinging leg is considered to be just touching the ground;

Step 2: According to the pressure sensor data obtained in Step 1 when the swinging leg is on the ground, perform adaptive adjustment of the ankle joint so that the foot of the swinging leg is completely on the ground;

Step 3: Read the gyroscope and accelerometer data of the inertial measurement module, calculate the pitch angle and roll angle of the sole of the foot, and then calculate the inclination angle a of the current slope and the angle b of the robot's forward direction relative to the slope, and take it to the right when facing the slope The direction of is the positive direction of the horizontal direction, and the b is the angle between the forward direction of the robot and the positive direction of the horizontal direction;

Step 4: According to a and b, configure the gait parameters, plan the next gait foothold and center of mass point based on the linear inverted pendulum model, and then perform online gait adjustment based on inverse kinematics; then switch the supporting leg to the swinging leg, The swinging leg becomes the supporting leg, and steps 1 to 4 are repeated to enter the next step of walking, so as to realize adaptive walking in a slope environment.

Further, the threshold Y in step 1=(0.01-0.05)*G, wherein, G is the gravity of the robot.

Further, the step two is specifically:

According to the pressure sensor data at the moment of landing, it can be judged whether the forefoot or the rear foot touches the ground first, and whether the left side or the right side touches the ground first, and then adjust the corresponding joints according to the following table:

initial contact sensor Robot up/downhill Adjustment method left front S1 uphill Pitch gives negative torque, roll gives positive torque right front S2 uphill Pitch gives negative torque, roll gives negative torque Left front S1, right front S2 uphill pitch gives negative torque left rear S3 downhill Pitch gives positive torque, roll gives positive torque Right rear S4 downhill Pitch gives positive torque, roll gives negative torque Left rear S3, right rear S4 downhill pitch gives positive torque Left front S1, left rear S3 walk horizontally along the slope roll gives positive torque Right front S2, right rear S4 walk horizontally along the slope roll gives negative torque 3 or more sensors walk horizontally No adjustment required

Further, the calculation formulas of a and b in the step 3 are as follows:

in, Indicates the pitch angle calculated by the inertial measurement module, and θ indicates the roll angle obtained by the inertial measurement module.

Further, the relationship between the foothold and the center of mass point of the biped robot walking on an inclined plane in the step 4 and the horizontal plane walking is as follows:

Among them, p _land,0 and p _cm,0 are the footing point and centroid point planning of the horizontal plane, respectively, and p _land and p _cm are the footing point and centroid point planning of the slope surface, respectively.

The beneficial effects of the present invention are as follows:

On the basis of realizing the original foot pressure detection function, the foot state detection device can detect the foot angle state, realize the slope information detection of the ground, and provide feedback for the biped robot to walk on the slope. The inclined plane walking method of the invention is simple to implement, and can effectively improve the walking stability and environmental adaptability of the biped robot.

Description of drawings

Fig. 1 is the circuit structure diagram of the main board of the foot state detection device in the present invention;

Fig. 2 is a schematic diagram of the structure of the foot state detection device and the installation position of the pressure sensor and the IMU in the present invention;

Fig. 3 is a schematic diagram of a biped robot walking along an inclined plane in a certain direction in an example of the present invention;

Fig. 4 is a flowchart of a method for walking on an inclined plane using the foot state detection device of the present invention;

Fig. 5 is a schematic diagram involving coordinate transformation in the present invention;

Fig. 6 is a schematic diagram of motion planning of a biped robot walking on an inclined plane based on a linear inverted pendulum model in the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the purpose and effect of the present invention will become clearer. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

As shown in Figure 1, the biped robot foot state detection device of the present invention includes:

Pressure sensor module: a pressure sensor module that uses resistance strain gauges to form a full-bridge circuit. It has the characteristics of high sampling accuracy and sensitive response, and is used to obtain the pressure of the installation point and the ground. The pressure sensor module includes four pressure sensors arranged around the feet, namely left front S1, right front S2, left rear S3 and right rear S4, for sensing the pressure between the feet and the ground.

AD conversion module: used to collect and convert the analog signal data output by the pressure sensor, and transmit it to the microcontroller. As one of the embodiments, the AD conversion module uses a 24-bit A/D conversion chip HX711, which has the advantages of high sampling accuracy and strong anti-interference.

Inertial Measurement Module (IMU): Contains a three-axis gyroscope and a three-axis accelerometer to measure the inclination angle of the soleplate of the foot. The inertial measurement module is arranged in the middle of the sole of the foot, its X-axis positively points to the front of the sole of the foot, its Y-axis positively points to the left side of the sole of the foot, and its Z-axis positively points upward. As one of the embodiments, the 6-axis IMU adopts the MPU6050 chip and is connected to the microcontroller through the I2C interface.

Communication module: used to realize the communication between the foot state detection device and the outside. As one of the embodiments, the RS485 bus communication interface is adopted, and the 485 chip adopts MAX485, while RS232, CAN bus interface and Bluetooth wireless communication mode are reserved.

Indication module: display the status of the system, use the green LED light to display the power supply, and the red LED light to indicate the system is abnormal.

Power module: used to provide stable DC voltage to each module of the system. As one of the embodiments, the system power source comes from an external power supply of 16V, and the power interface shares the same interface with RS485, including VCC, GND, 485+, 485-; respectively converted into 5V, 3.3 V.

Microcontroller module: used to read and process foot pressure sensor and IMU data, and transmit the data to the central controller of the biped robot through the communication module. As one of the embodiments, the microprocessor adopts STM32F103C8T6 chip, its main frequency is 72MHz, and it has abundant interfaces.

As shown in Figure 2, the foot state detection device in this embodiment is installed on the sole of the robot: the main board of the foot pressure detection device is fixed in the middle of the sole of the foot, and the four pressure sensors are fixed by cantilever beams, one end of which is fixed on the sole of the foot Four corners, the other end is in contact with the ground through the spikes. The IMU is arranged in the middle of the main board, its X-axis positively points to the front of the sole of the foot, the Y-axis positively points to the left side of the sole of the foot, and the positive Z-axis is vertically upward.

Figure 3 shows an example of the foot state detection device being applied to a biped robot walking on a slope. The slope angle of the slope is a=10°, and the included angle of the walking direction is b=100°.

A method for walking on an inclined plane of a biped robot, the method is realized based on the above-mentioned foot state monitoring device, and the method specifically includes the following steps (as shown in Figure 4):

Step 1: During the descending process of the swinging leg of the biped robot, adjust the ankle joint to be parallel to the horizontal plane, and detect the data of the four pressure sensors of the swinging leg to judge the footing: when any pressure sensor data Si>threshold Y is detected, At this moment, the swinging leg is considered to be just on the ground;

Preferably, the threshold Y=(0.01-0.05)*G, where G is the gravity of the robot.

Step 2: According to the pressure sensor data obtained in Step 1 when the swinging leg is on the ground, perform adaptive adjustment of the ankle joint so that the foot of the swinging leg is completely on the ground;

Specifically, the walking state of the biped robot can be judged according to the pressure sensor data when it just landed: 1) If the pressure sensor at the front sole has data for uphill, the pressure sensor for the rear sole has data for the biped robot to go downhill. Slope; if there are data on both the front sole and the rear sole, it means that the biped robot walks along the horizontal direction. 2) If the pressure sensor on the left side of the foot first has data, it means that the biped robot walks along the right side of the slope; if the pressure sensor on the right side of the foot has data first, it means that the biped robot walks along the left side of the slope; At the same time, there are data on the soles of the rear feet, indicating that the biped robot walks along the horizontal direction of the slope. Then adjust the corresponding joints according to the table below:

initial contact sensor Robot up/downhill Adjustment method left front S1 uphill Pitch gives negative torque, roll gives positive torque right front S2 uphill Pitch gives negative torque, roll gives negative torque Left front S1, right front S2 uphill pitch gives negative torque left rear S3 downhill Pitch gives positive torque, roll gives positive torque Right rear S4 downhill Pitch gives positive torque, roll gives negative torque Left rear S3, right rear S4 downhill pitch gives positive torque Left front S1, left rear S3 walk horizontally along the slope roll gives positive torque Right front S2, right rear S4 walk horizontally along the slope roll gives negative torque 3 or more sensors walk horizontally No adjustment required

Step 3: Read the gyroscope and accelerometer data of the inertial measurement module, calculate the pitch angle and roll angle of the sole of the foot, and then calculate the inclination angle a of the current slope and the angle b of the robot's forward direction relative to the slope, and take it to the right when facing the slope The direction of is the positive direction of the horizontal direction, and the b is the angle between the forward direction of the robot and the positive direction of the horizontal direction;

The specific calculation process is as follows:

As shown in Figure 5, where X _r Y _r Z _r is the horizontal coordinate system Σr, X _a Y _a Z _a is the intermediate coordinate system Σa, which can be obtained by rotating the horizontal coordinate system Σr around the x-axis by an angle a, X _b Y _b Z _b is the inclined plane coordinate system Σb, which can be obtained by rotating Σa around the x-axis by an angle b. Therefore, the rotation matrix of the horizontal coordinate system Σr to the inclined plane coordinate system Σb is

Suppose the Euler angles of the inclined plane coordinate system are in θ can be calculated from the gyroscope and acceleration data of the IMU, and the calculation method can adopt a common method in this technical field. Then the rotation matrix of the horizontal coordinate system Σr to the inclined plane coordinate system Σb is:

According to R=R _ab , get:

Hence:

in, Indicates the pitch angle calculated by the inertial measurement module, and θ indicates the roll angle obtained by the inertial measurement module.

Step 4: According to a and b, configure the gait parameters, plan the next gait foothold and center of mass point based on the linear inverted pendulum model, and then perform online gait adjustment based on inverse kinematics; then switch the supporting leg to the swinging leg, The swinging leg becomes the supporting leg, and steps 1 to 4 are repeated to enter the next step of walking, so as to realize adaptive walking in a slope environment. Fig. 6 is a schematic diagram of motion planning for a biped robot walking on an inclined plane based on a linear inverted pendulum model. Preferably, the relationship between the foothold and the center of mass of the biped robot walking on an inclined plane in step 4 and the horizontal plane walking is as follows:

Among them, the foothold point p _lan d _,0 and the center of mass point p _cm,0 of the biped robot walking on the horizontal plane can be planned using common methods in this technical field, which are well known to those skilled in the art; p _land and p _cm are respectively the slope Surface foothold and centroid point planning.

In summary, on the basis of detecting the foot pressure, the foot state detection device of the present invention also supports the detection of the angle of the bottom plate of the foot, which can be used to detect the inclination angle and walking direction of the inclined plane where the biped robot is located. The biped robot provides feedback when walking on an inclined plane, which effectively improves the walking stability and environmental adaptability of the biped robot.

Those of ordinary skill in the art can understand that the above description is only a preferred example of the invention, and is not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, for those skilled in the art, it can still be understood. The technical solutions described in the foregoing examples are modified, or some of the technical features are equivalently replaced. All modifications, equivalent replacements, etc. within the spirit and principles of the invention shall be included in the scope of protection of the invention.

Claims (7)

1. A foot state detection device of a biped robot, characterized in that the device comprises a pressure sensor module, an AD conversion module, an inertial measurement module, a communication module, a microcontroller module, a power supply module, and the pressure sensor module It includes four pressure sensors arranged around the feet, namely left front S1, right front S2, left rear S3 and right rear S4, which are used to sense the pressure between the feet and the ground; the inertial measurement module is arranged on the feet of the feet In the middle position of the bottom, the positive X-axis points to the front of the sole of the foot, the positive direction of the Y-axis points to the left side of the sole of the foot, and the positive vertical direction of the Z-axis is used to measure the inclination angle of the foot; the pressure sensor module and the AD conversion Module connection, the AD conversion module, inertial measurement module, and communication module are all connected to the microcontroller module, and the power supply module supplies power to all other modules; the microcontroller is used to process the pressure on the soles of the feet information and tilt angle, and transmit the data to the central controller of the biped robot through the communication module. 2. the foot state detection device of biped robot according to claim 1, is characterized in that, described pressure sensor is the pressure sensor that adopts resistance strain gauge to form full-bridge circuit; Described AD conversion module adopts 24 A/D conversion chip HX711, the inertial measurement module includes a three-axis gyroscope and a three-axis accelerometer, adopts an MPU6050 chip, and is connected to a microcontroller through an I2C interface; the described microprocessor uses a STM32F103C8T6 chip. 3. A method for walking on an inclined plane of a biped robot, characterized in that, the method is realized based on any one of the above-mentioned foot state monitoring devices, and the method specifically includes the following steps: Step 1: During the descending process of the swinging leg of the biped robot, adjust the ankle joint to be parallel to the horizontal plane, and detect the data of the four pressure sensors of the swinging leg to judge the footing: when any pressure sensor data > threshold Y is detected, this At that time, the swinging leg was considered to be just touching the ground. Step 2: According to the pressure sensor data obtained in Step 1 when the swinging leg is on the ground, perform adaptive adjustment of the ankle joint so that the foot of the swinging leg is completely on the ground; Step 3: Read the gyroscope and accelerometer data of the inertial measurement module, calculate the pitch angle and roll angle of the sole of the foot, and then calculate the inclination angle a of the current slope and the angle b of the robot's forward direction relative to the slope, and take it to the right when facing the slope The direction of is the positive direction of the horizontal direction, and the b is the angle between the forward direction of the robot and the positive direction of the horizontal direction; Step 4: According to a and b, configure the gait parameters, plan the next gait foothold and center of mass point based on the linear inverted pendulum model, and then perform online gait adjustment based on inverse kinematics; then switch the supporting leg to the swinging leg, The swinging leg becomes the supporting leg, and steps 1 to 4 are repeated to enter the next step of walking, so as to realize adaptive walking in a slope environment. 4. The method for walking on an inclined plane according to claim 3, characterized in that the threshold value Y=(0.01-0.05)*G in said step 1, wherein G is the gravity of the robot. 5. The slope walking method according to claim 3, characterized in that, described step 2 is specifically: According to the pressure sensor data at the moment of landing, it can be judged whether the forefoot or the rear foot touches the ground first, and whether the left side or the right side touches the ground first, and then adjust the corresponding joints according to the following table: initial contact sensor Robot up/downhill Adjustment method left front S1 uphill Pitch gives negative torque, roll gives positive torque right front S2 uphill Pitch gives negative torque, roll gives negative torque Left front S1, right front S2 uphill pitch gives negative torque left rear S3 downhill Pitch gives positive torque, roll gives positive torque Right rear S4 downhill Pitch gives positive torque, roll gives negative torque Left rear S3, right rear S4 downhill pitch gives positive torque Left front S1, left rear S3 walk horizontally along the slope roll gives positive torque Right front S2, right rear S4 walk horizontally along the slope roll gives negative torque 3 or more sensors walk horizontally No adjustment required 6. the inclined plane walking method according to claim 3, is characterized in that, the calculation formula of a and b in the described step 3 is as follows: in, Indicates the pitch angle calculated by the inertial measurement module, and θ indicates the roll angle obtained by the inertial measurement module. 7. The method for walking on an inclined plane according to claim 3, wherein the foothold of the biped robot walking on an inclined plane in the described step 4 and the relationship between the centroid point and the horizontal plane walking are as follows: Among them, p _land,0 and p _cm,0 are the footing point and centroid point planning of the horizontal plane, respectively, and p _land and p _cm are the footing point and centroid point planning of the slope surface, respectively.