Seven-degree-of-freedom manipulator model and control simulation based on adams and simulink
Recently, I was doing adams and simulink co-simulation, and found that there are few Chinese materials on modeling and simulation of high-degree-of-freedom manipulators on the Internet, and there is no open source model. Therefore, open source my learning results for everyone to learn and reference. The effect is not very good, and there are still many shortcomings. Please also forgive me.
github address
https://github.com/zzy5510/adams_simulink_robotarm
All codes and models are placed in the above warehouse. In the future, maintenance will be carried out and other control algorithms will be developed, such as adaptive control, optimal control and so on. If you think you are doing a good job, I hope to help you order a star.
Robotic arm model
The DH coordinate diagram of the robotic arm is as follows:
From the paper "An Adaptive Force Control Method for 7-Dof Space Manipulator Repairing Malfunctioning Satellite" by Brother Yang from the laboratory.
According to this figure, a manipulator model was established in Adams:
Note: In order to facilitate the calculation of inverse dynamics, the quality parameters of the rods are simplified. The mass of the rods 1, 3, and 4 perpendicular to the ground is set to 0, so that the rod The center of mass of the piece is located at the center of the horizontal section.
PD control
PD control proved to be stable. The mathematical principles and formulas of PD control are derived as follows: The
control block diagram is as follows: 
After experiments, it is found that the effect of this control method is very poor. I think that Lyapunov's second law only proves its stability, but the speed of convergence has not been proved. Due to the dynamic coupling between multiple joints, the acceleration of an independent joint is not only related to its own kinematic parameters, but also related to the parameters of other joints. Therefore, the effect of this control method is very poor.
Of course, it may also be related to my PID parameter not being adjusted properly.
Two-loop PID control
Three-loop PID control is a control scheme commonly used in industry. The desired position obtains the desired speed through the position loop PID, the desired speed is output by the speed loop PID to obtain the desired current, and the desired current is output through the current loop to obtain the actual current and output to the motor.
Since it is impossible to simulate the motor current in adams, the current loop is omitted, and the speed loop PID is considered to output the desired torque, which is directly applied to both ends of the robot arm joint.
The three-loop PID control is as follows:
Tuyuan paper "Research on Joint Control System and Trajectory Planning of Large-scale Robotic Arms in Space"
However, because of dynamic coupling, the effect of this kind of control is also very poor. Why can use current loop PID to achieve better results, but not torque?
This is because the current is proportional to the output torque of the motor. The torque coupling of other joints to this joint is very small through the action of the reduction gear. In this case, PID can achieve better results. However, if you use torque control directly, you cannot ignore the coupling effect of other joints.
In "Robot Modeling and Control", the explanation is as follows:
Inverse dynamics solution and control based on Newton-Euler iteration method
Newton's Euler method considers the dynamic coupling between joints. Knowing the joint angle and acceleration of each joint, the applied torque can be calculated to obtain the desired angular acceleration. This system establishes an improved DH coordinate system and obtains the Newton Euler iterative equation of the body coordinate system. The formula is as follows:
image source https://blog.csdn.net/qq_26565435/article/details/94303159
The control block diagram is as follows:
