Robot Control Apparatus for Dynamic Trajectory Velocity Matching
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Solution Overview
Problem
Existing control systems for industrial robots and NC machine tools face challenges in maintaining constant velocity and acceleration at the end point of a dynamically generated target trajectory, leading to irregularities in the processed surface quality, especially in multikind and small quantity production lines where setting precise machining programs is costly and difficult.
Innovation Solution
A control apparatus and method that dynamically adjusts the target trajectory using a Bezier curve interpolation, ensuring the TCP velocity at the end point matches the final target velocity by estimating the remaining distance and calculating optimal target acceleration, while limiting jerk and acceleration fluctuations to prevent surface irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the target trajectory is dynamically set in multikind and small quantity production, then production cost is reduced and versatility is improved, but manufacturing precision deteriorates due to difficulty in precisely calculating trajectory length and controlling velocity
Solution Approach 1:
The system performs preliminary calculation of the relationship between parameter values and trajectory length in advance, storing this data for later use. When dynamically setting the target trajectory, the control apparatus can quickly retrieve pre-calculated trajectory length information based on the selected parameter values, avoiding the need for complex real-time calculations and enabling precise velocity control even with dynamically changed trajectories.
Solution Approach 2:
The control apparatus continuously monitors the actual position and velocity of the movable unit, comparing it with the target trajectory and velocity profile. Based on this feedback, the system dynamically adjusts control parameters to maintain precise velocity control along the dynamically generated trajectory, ensuring manufacturing precision is maintained despite the adaptive nature of the system.
2Manufacturing precision
If velocity control is adjusted to maintain constant acceleration, then surface quality is improved, but control complexity increases due to the need for continuous calculation and adjustment of target acceleration
Solution Approach 1:
The system pre-calculates and stores the relationship between parameter values and trajectory length, which enables straightforward determination of target acceleration without complex real-time iterative calculations. This preliminary preparation significantly reduces control complexity while maintaining smooth velocity transitions for constant acceleration control.
Solution Approach 2:
The control apparatus dynamically adjusts the target acceleration based on the current parameter values and remaining trajectory length, creating a flexible control system that adapts to changing conditions. This dynamic adjustment maintains constant acceleration control for improved surface quality without requiring overly complex fixed control structures.
3Manufacturing precision
If the TCP velocity at the end point is maintained to match the final target velocity, then continuity and surface quality are improved, but calculation complexity increases due to the need for iterative solving of parameter values
Solution Approach 1:
The system pre-calculates and stores the relationship between parameter values and trajectory length, which provides a foundation for efficiently determining the parameter value that achieves the desired TCP velocity at the end point. This preliminary data preparation reduces the complexity of the iterative solving process by providing ready-reference information.
Solution Approach 2:
The control apparatus uses feedback from the actual TCP velocity and position to iteratively adjust the parameter values, converging on the optimal value that ensures continuity of velocity at the end point. This feedback-driven iterative approach maintains surface quality while managing calculation complexity through efficient convergence.
4Manufacturing precision
If acceleration is limited to prevent fluctuations, then surface quality and reliability are improved, but productivity decreases due to restricted movement velocity
Solution Approach 1:
The control apparatus dynamically adjusts the acceleration limits and target velocity profile based on the current position, remaining trajectory length, and selected parameter values. This dynamic control allows the system to operate at higher velocities when conditions permit while maintaining acceleration limits only where necessary to ensure surface quality, thereby improving overall productivity without sacrificing manufacturing precision.
Data Source
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AI summary
There is provided a control apparatus for controlling a device having a movable unit movable by a plurality of drive shafts. The control apparatus includes: target trajectory generation means for generating a target trajectory for a movement section defined by a start point and an end point; remaining distance estimation means for estimating a remaining distance along the target trajectory from a current position to the end point; acceleration calculation means for calculating an acceleration involved in varying a current movement velocity of the movable unit to a target velocity corresponding to a movement velocity to be satisfied by the movable unit at the end point of the target trajectory, such that a distance that the movable unit will have traveled substantially matches the remaining distance; and movement velocity updating means for calculating a new target movement velocity value by correcting the current movement velocity with the acceleration calculated.