Robot Servo Motion Curves for Gravity Center Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Robots experience instability and risk of falling due to sudden speed changes during motion, particularly when transitioning from a static to a moving state, as their joints are typically controlled at constant speeds, leading to abrupt acceleration and loss of gravity center.
Innovation Solution
A motion control apparatus and method that re-plans the rotation path of the servo joints by converting constant speed straight rotation into a curved path, using a motion curve calculated based on initial and target angles, and time, to reduce speed changes at the start and end of rotations, thereby stabilizing the robot's movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the robot joint is moved at a constant speed from angle a to angle b, then the motion is simple and easy to control, but the sudden speed change causes large acceleration that makes the robot unstable and likely to fall
Solution Approach 1:
The patent applies curvature to the motion trajectory by using a cubic Bezier curve instead of a straight line. The motion curve is defined by four control points that create a smooth curved path, ensuring that the speed changes gradually at the beginning and end of motion while maintaining constant speed in the middle portion. This curved motion profile eliminates sudden acceleration and deceleration, thereby preventing robot instability and falling.
2Productivity
If the robot joint is moved at a constant speed, then the control is straightforward, but the abrupt transition from static to motion state creates large acceleration that compromises robot stability
Solution Approach 1:
The patent implements dynamic speed adjustment by dividing the motion into three distinct phases: acceleration phase, constant speed phase, and deceleration phase. The cubic Bezier curve naturally provides this dynamic behavior, where the derivative (speed) is zero at the endpoints and reaches a maximum in the middle. This dynamic motion profile maintains high productivity through the constant speed phase while ensuring reliability by smoothly accelerating and decelerating, avoiding abrupt transitions that cause instability.
3Speed
If the robot joint uses a straight rotation path at constant speed, then the motion is efficient, but the sudden change in speed at start and end causes the robot to lose its gravity center
Solution Approach 1:
The patent uses a cubic Bezier curve to create a curved motion path instead of a straight line. This curved path ensures that the joint velocity starts at zero, increases smoothly to a maximum value, and then decreases back to zero at the endpoint. The curvature of the Bezier curve provides continuous acceleration and deceleration, preventing sudden changes in speed that would cause the robot to lose its gravity center and become unstable.
Data Source
AI summary
The present disclosure provides a motion control method and apparatus and a robot with the same. The method includes: obtaining a first rotational angle P1 of an output shaft of the servo currently at and a first time T1 for the output shaft of the servo to perform one rotation; obtaining a second rotational angle P2 for the output shaft of the servo to reach and a second time T2 for the output shaft of the servo to rotate from the first rotational angle P1 to the second rotational angle P2; calculating a motion curve B(t) of the output shaft of the servo based on the first rotational angle P1, the second rotational angle P2, the first time T1, and the second time T2; and controlling the servo to rotate according to the motion curve B(t). The present disclosure solves the instability in the gravity center of the robot.