CAN bus based on embedded system and the overhaul of the manipulator control system

This paper describes the embedded system and CAN bus based on the overhaul of the manipulator control system

Steam generator (Steam Generator) is a nuclear power plant in the first and second circuit connection between the hub and also the failure of the nuclear power plant running one of the largest equipment. Most of the steam generator failure was due to corrosion so that heat transfer pipe or tube to tube sheet joints leak, thus affecting the safe operation of power plants. Because there is radioactive material in the steam generator, when a leakage occurs, people can not access them for maintenance, then people need to replace the arm to complete the repair work. Maintenance system manipulator arm through six degrees of freedom within the steam generator repair and maintenance. The arm has six joints, six-axis; mainly used for steam generator (SG) of a loop side of the maintenance activities. Hand side arm with adapter, you can hang different maintenance tools to carry, you can steam generator as needed to implement different levels of maintenance.

As the robotic arm's work environment are unique, so the manipulator control system reliability throughout the higher demand, which needs good hardware design, more powerful microprocessors and better software Methods. In this paper, steam generator inspection manipulator six degrees of freedom for the application background, six degrees of freedom given hardware architecture, maintenance arm and upper and lower computer software design. The hardware processor using TI's TMS320LF2407 composition as the main control chip SMC controller, IPC as monitoring machine, SMC controller and monitor computer use CAN bus connection. Monitoring the main computer to complete manipulator control algorithms, data logging and real-time monitoring, SMC controller for manipulator control, sensor data acquisition and communication. In software, SMC controller uses μC / OS-II real-time embedded operating system, and modular program design, management and follow-up to facilitate software upgrades, the monitor computer use Visual C + + and OpenGL designed monitoring software.

A description of maintenance manipulator

Manipulator control system block diagram shown in Figure 1.

CAN bus based on embedded system and the overhaul of the manipulator control system


System is mainly distributed in three regions by the device component. (1) nuclear reactor plant in a container outside the distribution system and monitoring system; (2) is located near the SMC controller steam generator, the maximum distance up to 100m; (3) in the steam generator lower head in the vicinity of the machine arm body, repair tools, surveillance cameras, including container and SMC controller to reach maximum distance 150m.

Here are the three parts of the connection between the relationship and the main function.

(1) Container and SMC controller: ① distribution system from the container to the SMC controller 220VAC, 48VAC power output, etc.; ② container monitoring system and the SMC controller with fieldbus communication; ③ container monitoring system to the SMC control devices to provide remote reset (Reset) signal; ④ SMC controller to the container monitoring system to provide their own work status signal.

(2) SMC controller and manipulator body: ① SMC controller to the manipulator body respectively the DC servo motor servo drive PWM signal; ② SMC controller to the robot arm and rotate the body to provide intermediate frequency transformer excitation signal; ③ SMC controller to the machine arm body misalignment detection potentiometer to provide excitation signals; ④ R resolver angle to the SMC controller feedback signal; ⑤ error detection potentiometer provided to the SMC controller error detection signal.

(3) the container body and arm: ① from the container, bulk supply distribution system maintenance tools to the robot arm power, monitoring camera power supply, cooling unit power; ② SG surveillance camera near the container monitoring system to provide surveillance video.

As the manipulator control algorithm is high, control complexity, so use upper and lower bit machines distributed control method to design the control system.

2 hardware design

Manipulator control system has three main components, namely, IPC, SMC controller and manipulator body. IPC is mainly responsible for the manipulator control algorithm, inverse solution algorithm, working status display, data logging and real-time monitoring, maintaining and SMC controller, six joint panels of real-time communication; SMC controller is the direct control of the manipulator components It receives industrial computer through CAN communication transmission over the arm angle, velocity and acceleration information corresponding to the manipulator body control, while the manipulator joint angles, and operating parameters of CAN communication transmitted through the IPC, SMC control arm receiving bulk orders, and follow the instructions to make a mechanical movement, and angle of the signal back to the SMC controller.

2.1 SMC controller hardware circuit design

The hardware block diagram shown in Figure 2. The system processor uses TI's TMS320LF2407, it is TI's new high-performance 16-bit digital signal processor, a 24X a new member of the family, specifically for the control and motion control electrode digital realization of the design. Full compliance with CAN2.0 specifications, support 11 standard and 29-bit extended identifier, the system can meet the motor control and CAN communication.

CAN bus based on embedded system and the overhaul of the manipulator control system

(1) In order to joint the motor position feedback and improve control accuracy, make the system run more smoothly, the motor shaft and reducer installed respectively in a rotating position detector of transformers, rotary transformers - digital converter (RDC) for axis angle decoding, the joint position of 21 into the natural binary code sent to DSP, to achieve position feedback.

(2) Select the Swiss MAXON Motor Company's RE series of graphite brush DC motor, rated voltage of 24V, 24V switch power from a power supply. Motor drive axle with SA60 pulse modulation type op amp, schematic diagram shown in Figure 3. It to load 10A of continuous current, full-bridge amplifier available in a wide supply voltage range.

CAN bus based on embedded system and the overhaul of the manipulator control system

(3) Joint motor current detected by current Hall device, through the op amp input to the DSP's A / D conversion, the robot arm joint motor is used to detect over-current, thereby judging whether the block transfer joint motor.

2.2 Communication Interface

CAN bus is a serial data communication protocols, communication rates up to 1Mb / s, using optical fiber as a communication medium to ensure the communication speed and reliability. Data length of up to 8 bytes, which can meet the general system control command, work status and testing data communications requirements. while eight bytes will not take up the bus for too long to ensure the reliability of communication. According to the characteristics of the manipulator control system, the IPC set to master node manipulator joint control node responsible for communication between nodes on the joint control of unified management.

IPC and the manipulator joint control node with questions and answers between the means of communication, industrial control computer calculates the angle of each joint to pass joint control panel, control panel will arm joints after the angle of information to IPC, After the data exchange control board according to information received by the control arm angle. Between IPC and the joint control panel once every 0.1s to exchange data, industrial computer each time point according to information received, both positive and negative solution to calculate.

(1) CAN bus driver using PCA82C250, it is an agreement between the controller and the physical bus interface, the device provides differential transmit capability to the bus and the amount of CAN controller provides differential receive capability, schematic diagram shown in Figure 4 . CAN bus and the DSP interface circuit diagram shown in Figure 5.

CAN bus based on embedded system and the overhaul of the manipulator control system

CAN bus based on embedded system and the overhaul of the manipulator control system

(2) IPC and the DSP board CAN communication with CAN Interface Card PCI-5110, its role is to increase the CAN-Bus to the computer field bus interface functions.

3 software system design

Manipulator control system software design consists of two parts: the lower machines SMC controller to control software design and PC control software design.

3.1 lower computer software design

μC / OS-II is a microprocessor designed specifically for a preemptive RTOS, DSP system development with the traditional 相比, which uses multi-task management, task synchronization and communication between the characteristics, to a certain extent on improving system reliability and real-time, to meet the manipulator control system data acquisition, CAN communications and current collection of real-time requirements.

Software TMS320LF2407 the T0 timer interrupt source as the operating system clock, interrupt period of 1ms. Create a task position loop, velocity loop tasks, A / D conversion tasks, CAN communication task and angle acquisition, according to the work manipulator system characteristics and functional requirements, system task partitioning shown in Figure 6. systems of communication and synchronization between tasks of system services used in mailbox and semaphore messages. semaphore used to control the right to use shared resources and stimulate the production of other tasks, the message mailbox used to notify the task of production; the task of this system is divided into three types: regular tasks generated by the activation of other tasks without waiting for the task, the task generated by the interrupt trigger. Figure 6 also reflects the situation of the system, task scheduling .

Controller from the series of three rings, including two analog inner loop (current loop, velocity loop) and a control loop.

PID control algorithm for integrated control algorithm using integral and PID control algorithm with dead zone: Integral PID control algorithm can guarantee the separation system has fast response and a relatively high control precision; PID control with dead-mechanical device can exercise in place, the control action will not be frequent changes to avoid unnecessary mechanical wear. Both control algorithm robustness, high reliability and simple algorithm to meet the system's control requirements.

3.3 The main function of the system structure frame

In the main function using OSTaskCreate () function initializes the establishment of the task Task Init (), initialize the task to create a series of semaphores and mailboxes, wake-up clock interrupt task. The establishment of the task set ring, speed ring tasks, current loop task , A / D conversion tasks, CAN communication task and the point of collection and other tasks. In μC / OS-II real-time kernel framework for the entire program structure is as follows:

Viod main (void) / / main function
Hardware initialization;
OSInit (); / / initialization of the kernel
Call OSTaskCreate () to create initialization task Task Init ();
OSStart (); / / start multi-task scheduling
Viod TaskInit (void * data) / / Task initialization
Initialize the hardware clock;
Create a user task;
Regularly check the state of the system;
Watchdog timer reset;
ISR / / interrupt service routine
The value of Save processor registers;
OSIntEnter ();
Implementation of the interrupt function;
OSIntExit ();
Restore processor registers a value;
Interrupt return;


3.4 Industrial Computer Monitoring Software

Monitoring software functionality mode into the installation, work, debug mode. Work, the installation mode is divided into real and imaginary mode. Work process is already plugged into the tube plate toe arm holes and swelling, arm in the inverted state, blocking completion of the work tube and other testing process. Installation process is the arm into the manhole, installation of its four toes to Tube Sheet and swelling process. Three-dimensional virtual model is a computer simulation, does not control the actual robot arm. Real mode to control a variety of data and information issued by the controller of the robot arm to control the movement and operation, the actual arm position and orientation consistent with the three-dimensional simulation.

Monitoring software by function into five modules: user interface design, trajectory planning and motion control design, task management module design, 3D motion simulation module design and system maintenance and fault diagnosis module design. Software functional structure shown in Figure 8.

CAN bus based on embedded system and the overhaul of the manipulator control system

To meet the system control and simulation, OpenGL-based single-document application to achieve the monitoring software.

The main function of monitoring software as follows:

(1) Main Menu: including mode selection, operating mode selection, installation, maintenance work of choice.

(2) parameter settings: CAN communication set, arm PID control parameter settings.

(3) arm information display: the joint position profile information, CAN communication status, working status of sensors, joint control of electrical current.

(4) manipulator control: JOG single-joint control, JOY six joint linkage control, automatic operation control, joint control block.

(5) record mode and Data Analysis: Choice and records maintenance, path optimization.

Based on a practical engineering practice in the steam generator repair six degrees of freedom manipulator is studied through a large number of theoretical and practical debugging test, designed a complete robot arm control system. The entire system of control precision, reliability and dynamic / static properties, meet certain technical requirements, technical requirements can be completed well in various functions, and applied to practical work.

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