Serial Robot Joint Torque Control for Real-Time Tracking Precision
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Solution Overview
Problem
The high nonlinearity and couplingness of serial robots make it difficult to calculate the torque of each joint efficiently, which is a challenge for real-time control systems, especially for robots with higher degrees of freedom, as the processes are computationally complex and time-consuming.
Innovation Solution
A joint control method that uses a structure array to store joint attribute and motion information, allowing for efficient calculation of angular velocity and acceleration through inverse dynamics, thereby reducing the need to compute complex matrices like M, C, and G, and enabling iterative torque calculation for each joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the full dynamics equation with matrixes M, C, G is used to calculate motor torque, then the control accuracy is improved, but the computational complexity increases and execution time becomes too long for real-time control
Solution Approach 1:
The patent segments the dynamics calculation into two parts: (1) pre-computation of matrixes M, C, G offline to obtain simplified recursive formulas, and (2) real-time execution of these simplified formulas during control cycles. This segmentation allows the complex full dynamics equation to be solved offline, leaving only simple recursive calculations for real-time execution, thus resolving the contradiction between control accuracy and execution time.
Solution Approach 2:
The patent performs preliminary computation of the complex matrix operations (M, C, G) during system setup or offline programming phase. The results are stored as simplified recursive formulas that can be rapidly evaluated during real-time control. This preliminary action eliminates the need to compute complex matrices during the 1ms control cycle, enabling both high accuracy and real-time performance.
2Measurement precision
If the full dynamics equation is used for torque calculation, then the control precision is improved, but the algorithm execution efficiency decreases
Solution Approach 1:
The patent divides the dynamics calculation into offline preprocessing (computing matrixes M, C, G and deriving recursive formulas) and online execution (applying simplified recursive formulas). This segmentation maintains control precision by preserving the full dynamics model while dramatically improving execution efficiency during real-time operation.
Solution Approach 2:
The complex computational work of deriving and storing the recursive formulas is performed in advance during offline programming. During real-time control, only the simplified recursive evaluation is needed, which is computationally efficient. This preliminary action resolves the contradiction between control precision and algorithm execution efficiency.
3Adaptability or versatility
If the serial robot has higher degree of freedom, then the robot functionality is improved, but the computational burden for real-time control becomes unaffordable
Solution Approach 1:
The patent applies segmentation to the dynamics calculation by separating offline preprocessing from online execution. For high-DOF robots, the complex n-degree-of-freedom dynamics equations are processed offline to generate simplified recursive formulas, enabling real-time control despite the high computational burden that would otherwise result from directly evaluating the full dynamics equations.
Solution Approach 2:
The patent performs preliminary computation of the dynamics model parameters and recursive formulas during offline programming or system setup. This allows high-DOF robots to achieve real-time control capability, as the computationally intensive work is done in advance, leaving only efficient recursive evaluations for the actual control cycles.
Data Source
AI summary
The present disclosure provides a joint control method for a serial robot and a serial robot using the same. The method includes: performing a analysis on an end joint in the plurality of joints, and calculating the force of the previous joint acting on the end joint; performing a analysis on each of the other joints in the plurality of joints, and calculating the force of the previous joint acting on the joint; obtaining an angular velocity and an angular acceleration of each joint after obtaining the force of the previous joint acting on the joint, and calculating a torque corresponding to each joint; and projecting the torque corresponding to each joint to a motor corresponding to the joint to obtain a torque to be applied to the motor at a current time. In this manner, which improves the tracking precision of the end joint while reduces the tracking error.