Robot Joint Motion Control via Parabola Trajectory

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Solution Overview

Problem

Consumer and entertainment robots experience joint motion overshoot, stiffness, and mechanization due to simple linear control methods, affecting user experience.

Innovation Solution

A robot joint motion control method and apparatus that includes a key point obtaining unit, smooth joint point determining unit, joint motion trajectory calculating unit, and joint motion controlling unit, using a preset linear control model and parabola connecting formula to calculate and control smooth joint motion trajectories, avoiding overshoot and enhancing user experience.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If simple linear connecting control is used, then the control implementation is simple, but the joint motion causes overshoot and stiffness

Engineering Contradiction:
Improvecontrol implementation simplicityVSAvoidjoint motion smoothness
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent applies curvature by replacing linear connecting trajectories with circular arc trajectories. The circular arc trajectory is defined by calculating key points (start point, end point, and midpoint) and using them to generate a smooth curved path that eliminates the stiffness and overshoot problems of linear control while maintaining implementation simplicity through standardized circular arc calculations.

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Ease of manufacture

If disconnecting control is used, then the control implementation is simple, but the joint motion causes overshoot and shake

Engineering Contradiction:
Improvecontrol implementation simplicityVSAvoidrobot motion stability
Core Design Contradiction:
Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary action by pre-calculating the circular arc trajectory key points (start point, end point, and midpoint) before execution. The midpoint is specifically calculated in advance to define the curvature of the trajectory, allowing the control system to smoothly transition between joint positions without sudden disconnects that cause overshoot and shake.

Inventive Principle:
Principle #10Preliminary action

3Use of energy by moving object

If linear control model is used, then the control cost is low, but the joint motion lacks smoothness

Engineering Contradiction:
Improvecontrol costVSAvoidjoint motion smoothness
Core Design Contradiction:
Use of energy by moving objectVSEase of operation

Solution Approach 1:

The patent replaces linear control with circular arc trajectory control, where the trajectory is defined by three key points (start, end, and midpoint). This curved path approach significantly improves joint motion smoothness and eliminates the mechanized, stiff appearance of linear control while maintaining reasonable computational cost through efficient circular arc calculations.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Data Source

PatentUS11059173B2Robot joint motion control method, device and robot using the same
Publication Date: 2021.07.13 UBTECH ROBOTICS CORP LTD
  • US11059173B2 patent drawing
  • US11059173B2 patent drawing
  • US11059173B2 patent drawing

AI summary

The present disclosure provides a robot joint motion control method and apparatus as well as a robot using the same. The method includes: obtaining coordinates of a plurality of key points of a motion of a joint of the robot based on a preset linear control model; determining coordinates of two smooth connecting points respectively before and after each key point based on a preset time connecting factor; calculating a joint motion trajectory between each two adjacent smooth connecting points using a preset parabola connecting formula, based on the coordinates of the two smooth connecting points and the corresponding key point; and controlling the joint of the robot to move according to the joint motion trajectory between each two adjacent smooth connecting points. The present disclosure can avoid the joints of a robot from overshooting, thereby enhancing the user experience.