2. The difficulty of humanoid robot motion control is expected to increase significantly, which is expected to bring about increased market demand

2.1 Industrial robots usually use PC as the host computer to complete human-computer interaction/trajectory planning, and Based on PLC or PC-based controllers to achieve motion control through joint control, position control and force control

Industrial robots are widely used in the field of industrial automation. The control system is the core part of the robot, and its function and performance directly affect the final performance of the robot. Usually, the architecture of PC host computer + special motion controller is adopted, and PC is used as the host computer to complete human-computer interaction and motion trajectory planning. The special motion controller based on DSP and FPGA is mainly designed, in which DSP completes the scheduling of robot motion control tasks and realizes real-time control of robot joint space. FPGA is used for the design of the functional interface required by the control system. The trajectory planning and velocity control of the robot are realized in the cartesian coordinate space, and the linear and circular arc basic trajectory interpolation algorithm and the acceleration and deceleration calculation of S-shaped curve are available to improve the smoothness of the robot’s front end motion.

Trajectory planning directly determines the motion mode of the robot. Trajectory planning is based on work tasks and robot performance, to solve the time function of the amount of movement of the robot, such as human position and posture. The input is the expected trajectory, kinematics and dynamics parameters, and the output is the amount of movement of each joint or end actuator of the robot, including the time series of displacement, speed and acceleration. Trajectory planning of industrial robots is generally divided into basic trajectory planning and optimal trajectory planning, among which basic trajectory planning is divided into Cartesian space planning and joint space planning.

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Optimal trajectory planning usually considers efficiency, energy, stationary and other factors to find the optimal trajectory planning scheme required by each working condition environment: 1) Time optimal planning: the most common optimal trajectory planning requirements, usually through kinematic or dynamic constraints to find the optimal solution; Genetic algorithm and other optimization algorithms are used to solve the optimal solution. Transform the time model into other, more general models. 2) Optimal energy planning: on the one hand, it tries to find the smoothest trajectory to reduce the energy loss between joints; on the other hand, it also optimizes the energy distribution by optimizing the entire dynamic system. 3) Optimal impact planning: On the one hand, the purpose is to reduce the impact of the robot in the process of movement, to a large extent can reduce the error of track tracking, on the other hand, can greatly reduce the resonance, jitter, mechanical wear, service life reduction and other defects caused by excessive impact, so that the robot can run stably and smoothly. 4) Hybrid optimal trajectory planning: two or more optimality optimization schemes are considered comprehensively, among which the time-energy optimal trajectory research takes the longest time and is also the two most demanding indexes in industrial production. There are many classifications of industrial robots according to different structural forms, uses and operational requirements, but the control is mainly based on multi-axis real-time motion control, and the task is completed based on joint control, position control and force control.

1) Joint control: Joint control is the most basic and core control process of industrial robots. Single-joint control does not consider the influence between joints, and the mechanical inertia of the robot is treated as a disturbance item. It is usually driven by a motor, and closed-loop control is formed by current detection, speed detection and position detection.

On the basis of single joint control, the influence between joints should be considered. Usually, the influence of other joints on the current joint is introduced into the position controller as a feedforward item, so as to form a multi-joint control system.

2) Position control: Position control of industrial robots is closely related to joint space trajectory. Taking six-degree of freedom industrial robots as an example, Cartesian position control can be used to realize the end movement of industrial robots in accordance with the given position and attitude through the given position, joint space position conversion and 6-way single-joint position controller.

3) Force control: Multi-dimensional force sensor is used to obtain multi-dimensional force and torque information in Cartesian coordinate system. Multi-dimensional force sensor is mainly composed of force sensor, signal acquisition circuit, signal conditioning circuit, multi-dimensional signal decoupling system (hardware or software decoupling), upper computer or embedded system information processing software, etc.