CN1586829A - Plug-and-play mechanical arm system based on distributive control - Google Patents

Abstract

A plug-and-play manipulator system based on distributed control, used in the field of robotics. The invention includes: a host, a USB interface module, a central controller, an internal distributed control system and a mechanical arm body. The host is connected to the USB interface module through a USB cable. The central controller is located between the USB interface module and the internal distributed control system. Both parts are connected to the central controller through a parallel bus. The internal distributed control system consists of multiple Subsystems with the same function are connected in parallel. Each subsystem includes a PID controller, a DC motor driver and a DC motor with feedback. The internal distributed control system is directly connected to the manipulator body through control lines. The invention provides a complete solution to the interface problems and control problems encountered in the development of popularization of robots in the future.

Description

Plug and Play Manipulator System Based on Distributed Control

technical field

The invention relates to a universal manipulator system, in particular to a plug-and-play manipulator system based on distributed control. Used in the field of robotics.

Background technique

Nowadays, robot technology has formed an emerging industry with broad development prospects, especially miniaturized and intelligent robots have become one of the latest robot research directions. Among them, the robot manipulator (mechanical arm) has developed rapidly, and its application scope has gradually penetrated from the original industrial environment to all walks of life in society. It is conceivable that in the future, ordinary users will have a small intelligent robotic arm at home like other electrical appliances. , to help humans complete some specific tasks. However, although the robotic arm technology has made a lot of progress in the past few decades, it is still far from daily life, mainly due to the complex mechanism of the robotic arm, the high price, the complicated interface method, and the difficulty in ensuring the control accuracy.

With the increase of peripheral sensors of the manipulator, the transmission data between the manipulator and its controller (typically a personal computer) will greatly increase (such as video transmission, sonar, infrared, etc.), and the traditional computer interface cannot meet such needs. At present, the USB interface has gradually become a standard configuration and is accepted by the majority of computer manufacturers, and it has gradually become the first choice for the host peripheral interface with the characteristic of the highest transmission rate of 480Mbits/sec. At the same time, distributed control technology has become the mainstream technology of high-precision robotic arm motion control. It can make multiple modules with the same function work at the same time without affecting each other and improve control accuracy. However, so far, almost all robotic arm application systems are connected to the console using RS23 or dedicated control lines, and the data transmission speed is limited; while the control part of the joint is open-loop control, which cannot meet precise control, and closed-loop control requires Most of them need to be equipped with a special control box, which is not suitable for home use and miniaturization of the system.

After literature search, it was found that Chinese patent application number 03115472, title: personal manipulator system based on universal serial bus interface, this patent system can realize the control of the manipulator by the host through the USB interface, and supports hot swapping. However, the USB interface of this system adopts the 1.1 specification, and the transmission speed cannot meet the occasions with high transmission speed (such as real-time video transmission, etc.); moreover, the control of several joints of the mechanical arm adopts simple open-loop control (the drive is a steering gear) , so it can only be applied to occasions with relatively low technical requirements, and cannot achieve precise control of the robotic arm.

Contents of the invention

The purpose of the present invention is to provide a plug-and-play manipulator system based on distributed control, which has greater flexibility and higher control performance, and the manipulator interface meets the requirements of the manipulator control process. A large number of sensing and control data transmission requirements, and can be applied to most personal computers, making the manipulator a general-purpose computer peripheral device, which can be applied to multiple fields such as home and mobile robots. This invention can use a relatively simple method to make the robot arm reach a certain control accuracy, and can complete daily tasks (clamping objects, etc.), and then achieve the goal of popularizing the robot arm.

The present invention is achieved through the following technical solutions. The invention includes: a host, a USB interface module, a central controller, an internal distributed control system and a mechanical arm body. The host is connected to the USB interface module through a USB cable. The central controller is located between the USB interface module and the internal distributed control system. Both parts are connected to the central controller through a parallel bus. The internal distributed control system consists of multiple Subsystems with the same function are connected in parallel. Each subsystem includes a PID controller, a DC motor driver and a DC motor with feedback. The internal distributed control system is directly connected to the manipulator body through control lines.

In the internal distributed control system, the input interfaces of the PID controllers of all subsystems are connected in parallel and connected to the central controller through the same parallel bus, and the output of each PID controller is the steering control signal of the DC motor and the control current speed. PWM (Pulse Width Modulation) waves, these two outputs (two control lines) are directly sent to the DC motor driver, so that the DC motor driver can drive the DC motor to do corresponding movements. There is an incremental encoder disc at the end of each DC motor, which immediately sends the feedback signal of the motor movement to the PID controller, thus forming a complete closed-loop system, which can realize the precise PID control of the position and speed of the motor. In the distributed control system, each subsystem operates independently, except that the input of the PID controller is connected to the central controller through the same parallel bus, and there is no other part that interferes with each other or interferes with each other. The DC motor driver in the present invention adopts a dedicated DC motor drive chip to realize bipolar control of the DC motor. This control mode can obtain shorter control response time and higher safety.

The body of the robotic arm is designed with lightweight aluminum alloy and is driven by 5 DC motors. The main drives of shoulder joints, elbow joints, wrist joints and claws are all driven by high-precision gears to ensure the accuracy of movement. In addition, it is equipped with a base, which is convenient for the mechanical arm to rotate 360 degrees in the plane. The base is connected to the upper part of the mechanical arm through a plane bearing, the motor is installed on the upper part of the mechanical arm, and the output shaft of the DC motor is fixed to the base through a pin.

The invention is connected with the host through a USB cable, and the user can set the relevant parameters of the mechanical arm on the PC terminal. On the host side, an external network camera is installed to monitor the operation of the robotic arm system in real time. When working, the user first sets the motion parameters (including PID parameters, desired motion position, speed, etc.) of each joint of the present invention on the host computer. This corresponds to different tasks for each DC motor. After that, the user will send these tasks to the USB interface module of the robotic arm through the USB interface according to his own protocol. When the USB interface module receives the data, it will notify the central controller that it has received the user data. The central controller will read these data from the USB module and analyze and process them. The central controller will separate these data into specific tasks corresponding to each joint according to the protocol defined by the user on the PC side. Finally, the central controller sequentially assigns each task to the corresponding PID controller in the internal distributed control system, so that the PID controller will control the motor movement by itself without being controlled by the central controller. During the operation of the motor, the PID controller will finally feed back its own state information to the host according to the above inverse process to complete the control of the entire robotic arm. USB was initially used as an industry standard to expand the existing architecture of the host computer, mainly used in consumer and commercial fields. Compared with other computer peripheral interfaces, the USB interface has many advantages. The invention uses a USB interface module to connect with the host, and the host can easily install and configure new equipment after the equipment is connected to the system, and can also dynamically change equipment parameters. This feature can meet the flexibility required by the personal robotic arm. It can be easily and dynamically disconnected from or connected to the host. The host will automatically determine whether the robotic arm is connected and display this information to the user of the robotic arm. In this way, the host and the robotic arm together realize the plug-and-play function of the robotic arm, adopt the latest USB2.0 standard, and can also obtain faster transmission speed and have the characteristics of backward compatibility.

In the present invention, an internal distributed control system is embedded, and the entire control system is divided into several independent subsystems according to functions. As mentioned above, each subsystem consists of a PID controller, a DC motor driver, and a DC motor with feedback. Each subsystem is called a node. All nodes are connected with the central controller of the present invention through a parallel bus. Because the motor control tasks in each node are independently completed by its PID controller, the load on the central controller will be relatively low, and it is only responsible for data transmission control and task assignment. This working mechanism will significantly reduce the control complexity of the system, and improve the reliability and control performance of the entire system at a small cost. At the same time, it closely combines upper-level planning with lower-level motion control, providing conditions for real-time control. The present invention models the control system of the manipulator by using the distributed control technology, establishes an easy-to-use, robust and general-purpose distributed control system of the manipulator, and transforms the centralized task processing of the host in the original control system For the step-by-step processing of the bottom robot arm, the coupling between objects is reduced, which provides convenience for the effective realization of the entire system.

The invention realizes the plug-and-play function and precise control of the universal mechanical arm through the high-speed USB2.0 interface and distributed control, and finally realizes the miniaturization and generalization of the applicable mechanical arm. Compared with the background technology, the precise control of the mechanical arm is finally realized by utilizing the characteristics of modularization and high reliability of the internal distributed control system. The present invention provides a plug-and-play and distributed control solution for a general-purpose robotic arm, and provides specifications and references for architecture and technical realization for the research and development of future household robots and distributed robots, so that each robot research and development institution can refer to this Yigui independently developed a robotic arm similar to ordinary computer peripherals, thereby improving research efficiency and promoting the development of robotics.

Description of drawings

Fig. 1 structural representation of the present invention

Fig. 2 functional block diagram of the present invention

Fig. 3 PID control module control block diagram of the present invention

The hardware interface connection diagram of Fig. 4 single-chip microcomputer of the present invention

Fig. 5 flow chart of the main program of the single-chip microcomputer end of the present invention

Detailed ways

As shown in FIG. 1 , the present invention includes: a host 1 , a USB interface module 2 , a central controller 3 , an internal distributed control system 4 and a robot arm body 5 . The host 1 is connected to the USB interface module 2 through a USB cable, and the central controller 3 is located between the USB interface module 2 and the internal distributed control system 4. These two parts are connected to the central controller 3 through a parallel bus, and the internal distributed The control system 4 is composed of multiple subsystems with the same function connected in parallel, wherein each subsystem includes a PID controller 6, a DC motor driver 7 and a DC motor 8 with feedback, and the internal distributed control system 4 directly passes through The control line is connected with the mechanical arm body 5 .

In the internal distributed control system 4, the input interfaces of the PID controllers 6 of all subsystems are connected in parallel and connected to the central controller 3 through the same parallel bus, and the output of each PID controller 6 is the steering control signal of the DC motor 8 And the PWM wave that controls the current speed, these two control lines are directly connected to the DC motor driver.

There is an incremental code disc at each DC motor 8 end. On the host computer 1 side, an external network camera 9 can also be set.

Embodiment is provided below in conjunction with accompanying drawing:

The present embodiment is a 5DOF (degree of freedom) small-sized mechanical arm. The universal mechanical arm body 5 is made of hard aluminum alloy, with a height of 15 cm, a width of 45 cm, and a mass of 1.8 kg. Each joint is directly driven by five DC motors 8. Both are equipped with a Ni-MH battery and control board. The speed control of DC motor 8 in this system adopts PWM (pulse width modulation) mode. Fig. 1 shows the hardware structure diagram of the universal manipulator, wherein the USB interface module 2 realizes the interconnection between the universal manipulator and the host computer 1, and its related configuration is controlled by the central controller 3 (an 8-bit single-chip microcomputer) through an 8-bit parallel bus Finish. In addition, the central controller 3 is connected with five PID control subsystems in parallel to realize the closed-loop control of the DC motor 8 . The external camera 9 connected to the host end can collect the observed moving image of the mechanical arm into the control software in real time.

In this embodiment, the USB2.0 high-speed interface chip ISP1581 is used to realize the connection between the universal robot arm and the host computer 1 . This chip supports both the USB2.0 specification and the USB1.1 specification, and it communicates with the MCU through an internal 8-bit bus. Central controller 3 is an enhanced 51 single-chip microcomputer PC89C61. In addition to all the functions of ordinary 51 single-chip microcomputers, this single-chip microcomputer has 256Byte RAM and 16Kbyte ROM, which can basically meet the needs of more variables and longer codes in this example program. Figure 4 shows how it is connected to peripheral devices.

PID controller 6 is a motor-specific control chip that supports position control and speed control. It supports a position range of -1,073,741,823 lines to +1,073,741,823 lines, and a speed range of 0 to 11,073,741,823/216 lines/sample. Before the motor moves, only the central controller 3 needs to set the parameters of the LM629, including Kp, Ki, Kd, expected position and expected speed, etc., and then start. After that, LM629 will send corresponding PWM (pulse width modulation) wave to DC motor driver 7-LM298 after internal operation. LM298 is a latter that will drive the DC motor 8 at a speed specified by PWM and stop at an appropriate position. After the single-chip microcomputer configures the PID controller 6, it can continue to perform other tasks, and the entire PID operation process does not need its intervention.

Figure 2 shows the overall functional diagram of the system. The host is used as a platform for the user to control the general-purpose robotic arm. During the operation of the system, a user interface needs to be run on the host to receive the user's settings for the robotic arm and task assignments. At the same time, it can realize the function of displaying the running status of the universal robotic arm in real time. . After the relevant settings and tasks are sent to the central controller through the USB interface, the central controller will do corresponding processing according to the received data, such as PID controller parameter setting, DC motor motion parameter setting, stop motor, start motor and so on. At the same time, it needs to feed back the status information of each PID controller to the host in real time for the latter to display to the user. The feedback signal includes the connection status of the PID controller, the position, speed, acceleration, etc. of the motor. After the single-chip microcomputer decomposes the task, it will send configuration instructions to the relevant PID controller, and the PID controller will take control of the motor driver according to the instruction. If it is a running instruction, it will send the corresponding PWM wave to the motor driver. If it is a stop instruction, it will will turn off the motor driver. During the operation of the motor, it needs to send its own state to the PID controller through the encoder to realize the closed-loop control of the motor. The block diagram of the PID control is shown in Figure 3. Figure 4 shows the hardware interface connection diagram of the microcontroller. Two 8-bit parallel ports are used to connect the ISP1581 and the PID controller respectively. The main program flow chart of the central controller is shown in Figure 5. After the system starts, it will first initialize the relevant parameters of the USB interface device, including device descriptors, data transmission standards and other interface parameters. Then, the central controller will initialize the PID control device LM629 one by one: set the zero point, set Kp, Ki, Kd parameters, etc. In this way, the entire initialization process ends here, and the program will enter a loop, waiting for the command sent by the PC, and the loop will be interrupted after receiving the command, and the next step will be processed according to the command. When the robotic arm is connected to the host, the host will send relevant requests to the central controller through the interface device ISP1581 according to the USB specification. After receiving the response, the host will notify the operating system of the device-related information and establish a communication channel with the universal robotic arm. During the establishment of the USB communication channel, the central controller is responsible for the parameter configuration of the ISP1581 and the response to the USB request, and all data are transmitted bidirectionally through the ISP1581. During the cycle of the central controller, in addition to the USB request command, it may receive two other commands from the host: motion command and query command. The motion command includes all the data that the user expects the motor to move (movement mode, position, speed, acceleration, etc.), and the central controller needs to configure the corresponding PID controller according to the command and start it. After that, it also needs to notify the PC of the state of the target motor , for the user to do the next step. The query command allows the user to obtain the status information of each joint of the robotic arm at any time. This function ensures the transparency of the universal robotic arm to the user and provides a guarantee for the realization of precise motion control of the robotic arm. If an abnormal situation occurs in the system during the movement of the universal robotic arm, it will stop the movement and report the error to the host in real time, waiting for the user to deal with it accordingly.

The universal manipulator example of the present invention establishes an easy-to-use, robust, and universal manipulator control system, and realizes plug-and-play and precise control of the manipulator. The entire system fully embodies the flexibility of the USB interface and the advantages of the distributed control system in the control of the manipulator in terms of hardware and software structures, and also provides a specific implementation method for the development of the future universal manipulator according to the invention.

Claims (4)

1, a kind of plug and play mechanical arm system based on distributed control, comprise: main frame (1), central controller (3), inner dcs (4) and mechanical arm body (5), it is characterized in that, also comprise: usb interface module (2), main frame (1) is connected with usb interface module (2) by a USB connecting line, it is middle with inner dcs (4) that central controller (3) is positioned at usb interface module (2), these two parts all are to be connected with central controller (3) by parallel bus, inner dcs (4) is made of a plurality of subsystem parallel connections with identical function, wherein, each subsystem all comprises a PID controller (6), the direct current generator (8) of a DC motor driver (7) and a band feedback, inner dcs (4) directly is connected with mechanical arm body (5) by control line.

2, according to right 1 described plug and play mechanical arm system based on distributed control, it is characterized in that, in the inner dcs (4), the input interface of the PID controller (6) of all subsystems is connected in parallel, be connected to central controller (3) by same parallel bus, and each PID controller (6) is output as the pulse width modulated wave of direct current generator (8) steering controling signal and control electric current rotating speed, and this two-way control line is directly connected on the DC motor driver (7).

3, according to right 2 described plug and play mechanical arm systems, it is characterized in that each direct current generator (8) end all has an increment type coding disk based on distributed control.

4, according to right 1 described plug and play mechanical arm system, it is characterized in that,, an external network camera (9) is set at main frame (1) end based on distributed control.

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