Controller belongs to the brain of industrial robot. The quality of its design has a direct impact on the performance and accuracy of industrial robot. Six-axis industrial robots are one of the types of industrial robots. The complexity of motion control is relatively high. From the point of view of the existing motion controllers in China, they can not effectively meet their control needs. Based on this, on the basis of DSP, this paper analyses the method of designing the controller of six-axis industrial robot, aiming at effectively controlling the operation of six-axis industrial robot and exerting its application value.
After the application of industrial robots in manufacturing field, the production efficiency has been obviously improved, and the degree of informatization and industrialization of the industry has been enhanced so as to realize the prosperity and development of the manufacturing industry. With the widening of the application field of industrial robots, the research on industrial robots and their controllers has gradually increased, and good research results have been formed. When a six-axis industrial robot moves, it is necessary to control the six-axis linkage scientifically. Because the existing controllers can not meet the requirements of real-time and accuracy, it is necessary to study the six-axis industrial robot on the basis of corresponding technology. Therefore, the research in this paper has very important practical significance. When the performance of industrial robots is realized, the controller plays a key role. Through its hardware and software platform, it provides good support for the motion control of industrial robots. From the user’s point of view, the controller is similar to the black box. When users use the controller, they only need to input the start, target position and path constraints of the trajectory into the host computer. After that, the controller can automatically complete the trajectory planning according to its own functions, and control the end-effector to make the trajectory pre-determined.
First set the same. Firstly, a joint corresponds to a servo system. When each joint moves, the hardware structure should make its motion coordinated and compatible with each servo system. Secondly, when planning the motion trajectory, the algorithm needed is more complex, such as calculating interpolation points, forward and inverse kinematics, and the amount of coordinate transformation and matrix inverse calculation is not enough. Usually large, the hardware architecture should give good support to this; third, when controlling six servo systems, there are more I/O ports needed, and users have secondary development needs. Therefore, the number of I/O with the hardware architecture should be enough, and can be reserved to meet customer needs. In the circuit board, the important component is power supply, which is related to the stable realization of the circuit board function. When designing power supply, it should be based on the type of circuit board. In this paper, the power supply needed to be designed is used in the controller, that is to say, the power supply of DSP needs to be designed. Generally, there are three kinds of power supply circuits for DSP. The first one is the nuclear power supply in the DSP chip, with 1.9V as the supply voltage; the second one is the I/O port power supply, with 3.3V voltage, which does not need to be converted; the third one is the analog circuit power supply, which belongs to the special power supply for ADC module, thermostatic element with 3.3V voltage. Because of the large number of power supply, we need to focus on the power-on sequence. For DSP, the power-on, power-off sequence and reset problem need to be properly designed. Ideally, in the DSP chip, the internal nuclear power supply and I/O port power supply should be powered on at the same time, but because it is very difficult to realize in practice, the I/O port power supply and analog circuit power supply should be powered on first, and then the internal nuclear power supply should be powered on. Based on this power-on sequence, LT1963A-33 is chosen as the chip model in the design. When the controller controls the six-axis industrial robot, data exchange between PC and DSP is needed to effectively mobilize the joints and ensure the normal operation of the robot. Generally, the realization position of the human-machine interface of the control card is the upper computer.
For the control card itself, the motion trajectory planning algorithm needs to be implemented in real time. Therefore, the amount of data exchanged between the upper computer and the control card is very large. In order to ensure the normal communication, a very high transmission rate and real-time performance are required. At the beginning of the design, the linear interpolation point and arc interpolation point have been written into the DSP. PC only needs to send the trajectory motion command to the DSP. Thus, the complexity of the upper computer program can be reduced effectively, and the communication between them can be simplified. Panasonic A5 servo system is used as the servo module in this paper. Firstly, the optocoupler module is designed. Its main function is output, input control servo driver signal, such as input servo ON, output servo preparation, etc. In some controllers, this module is used to control servo driver, reaction servo working state, etc. Because the servo driver is in a bad working environment, the interference is large, when designing. Anti-interference design is also needed. When the optical coupler transmits the electrical signal, the medium is light, which can isolate the input and output signals well. It is widely used in industry. In this paper, TLP521-4 is used when the optical coupler isolates the input and output ECG. Secondly, the differential signal conversion module is designed. When the servo driver outputs, there are three phases: A phase, B phase and Z phase. When each phase outputs, the differential signal is a group of differential signals. The differential signal has very strong anti-jamming ability, and can be highly immune to external electromagnetic interference. Moreover, it does not need to rely on “ground” to improve transmission reliability. When designing the module, the differential signal can be highly immune to external electromagnetic interference. The chip used is MC3486. Finally, the analog output module is designed. The speed mode is the mode chosen by the servo driver when working. In order to control the speed of the motor, it is necessary to receive analog signals. When realizing this function, the digital-to-analog conversion circuit method is adopted. If the special D/A chip is used, the design cost of the controller will be greatly increased, and the I/O connection occupied will be occupied. There are many ports. In the design process of this paper, the D/A conversion constitutes the application of PWM mode, that is, pulse width modulation mode. In the controller, there are two parts: the upper computer and the lower computer. The lower computer controller is the focus of this paper. Therefore, the upper computer function of the motion control system has not been fully developed. When the control system is mature, the functions of human-computer interaction interface and trajectory planning need to be realized on the upper computer. The interpolation algorithm, data communication and servo control are mainly completed by the lower computer. If the forward and inverse kinematics are not carried out on the upper computer, it can also be carried out by the lower computer. Specifically, control algorithm, data storage, data communication, servo control, I/O control and servo interruption are the overall software architecture of the controller design. Some of these software modules run on DSP and some on other chips to realize the functions of the controller. The controller designed in this paper belongs to the primary stage product. Linear interpolation points and arc interpolation points have been designed into the internal of the DSP beforehand. These points belong to the ideal position of each joint of the six-axis industrial robot. The actual position of the joint axis needs incremental coding and decoding. After that, the DSP receives the actual position information and makes a comparison. In order to control the servo system and minimize the directional motion error of the end effector, the position error is calculated, the joint feed speed is adjusted accordingly, and the relevant information is output. In order to facilitate program adjustment, a SRAM chip, IS61LVL416, is expanded in the data storage module. The chip has a large storage capacity. When debugging the DSP, it will be directly affected by the ARSM chip. When testing the performance of SRAM chip, we need to go through a series of procedures. From its overall process, we can see that the address starts from 0 and writes 0-0xFFFFFF data sequentially until the address is 0xFFFF. During this period, the verification work is carried out sequentially. After the test is completed, in order to understand the error information, we can check the error value of the variable, and finally make the performance of the chip. Judgement. Incremental photoelectric encoder is widely used in servo control system because of its high accuracy, fast response speed and stable performance. When the encoder outputs, the digital quantity can not be output directly.
The pulse signals of phase A, phase B and phase Z can be output. After processing, the information of rotor rotation and speed can be obtained. On the basis of rotor rotation and steering, incremental encoder can output a series of pulse signals. The more the rotation angle, the more the number of pulse signals output. Therefore, the faster the speed, the higher the pulse frequency. The actual position information of the joint axis needs to be decoded by incremental encoder, and the corresponding decoder should be designed for the encoder. The so-called dual-port RAM refers to adding data lines to SRAM chips, and both ends are independent buses. For internal storage data, shared by two ports, access time of storage space is not limited. Based on this, two separate CPUs are designed at both ends of the port. When accessing storage space, two CPUs belong to simultaneous asynchronous access to achieve data listening. In the process of sharing, in order to prevent the existence of data conflicts, it is necessary to add the arbitration mechanism into the arbitration mechanism to ensure the normal operation of the controller by exerting the relevant functions of the arbitration mechanism. In the process of building dual-port RAM, the memory block, M9K, is used to communicate smoothly with the DSP and improve the efficiency of the port. When the positive and negative limit positions are designed into the controller, the safety of the six-axis industrial robot can be effectively guaranteed. In the actual working process, if the motion of the joint axis is in the limit position, it will immediately stop running the motor corresponding to it. At the same time, the motor will not receive any forward signal, and can normally receive the reverse motion signal, so as to ensure the safety of operation. CONCLUSION: After designing the controller based on the above methods, it can effectively meet the basic requirements of the six-axis industrial robot in power control. However, due to the limited research capacity of this paper and the continuous development of science and technology, more in-depth research is needed.