PLC Target Command Control in Working Coordinates
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Solution Overview
Problem
Conventional model predictive control techniques for target devices struggle to optimize the trajectory followed by servo-controlled systems due to reliance on generalized coordinates, leading to errors and reduced follow-up capacity, especially when encountering obstacles.
Innovation Solution
A control device employing model predictive control within a predetermined working coordinate system, utilizing inverse kinematics and a target model to calculate target commands for each control axis, while incorporating probabilistic potential fields to avoid collisions, and adjusting parameters to minimize errors and optimize follow-up capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If model predictive control is optimized with reference to generalized coordinates, then it is easy to set the predictive model, but the trajectory traced by the output may vary complicatedly and is not always optimized
Solution Approach 1:
The patent inverts the conventional approach by performing model predictive control optimization in the working coordinate system (output space) rather than in the generalized coordinate system (joint space). This inversion allows the control optimization to directly affect the output trajectory, ensuring it is always optimized while maintaining ease of model setting through the working coordinate system representation.
2Adaptability or versatility
If both state quantity of working coordinate system and state quantity of generalized coordinate system are employed in predictive model, then more comprehensive control is achieved, but the Jacobian matrix does not provide correlation between position and angle, causing error to increase with progress of servo control
Solution Approach 1:
The patent extracts and eliminates the problematic Jacobian matrix transformation from the control system. By performing model predictive control directly in the working coordinate system without relying on Jacobian-based transformations between coordinate systems, the patent removes the source of position-angle correlation errors while retaining comprehensive control capability through direct working space optimization.
3Device complexity
If conventional feedback control is used, then the control system is simple, but response delays occur in each servomotor causing the actual trajectory to deviate from the command trajectory
Solution Approach 1:
The patent applies preliminary action by using model predictive control to pre-calculate optimal control inputs that anticipate future trajectory requirements and compensator for expected delays. This allows the system to proactively adjust for response delays before they cause trajectory deviation, improving response speed while maintaining reasonable control system complexity through the predictive framework.
Data Source
AI summary
A control device is configured to cause an output of a target device to be servo-controlled to follow a predetermined command in a predetermined working coordinate system. The control device includes: a target model controller that possesses a target model in which the target device is modeled based on the predetermined working coordinate system and simulates and outputs an output according to the predetermined working coordinate system by using the target model; a model predictive controller that possesses a predictive model in which a correlation between a predetermined state variable that is related to the target model possessed by the target model controller and based on the predetermined working coordinate system and a control input to the target model controller is defined in a form of a predetermined state equation based on the predetermined working coordinate system; and a calculator that calculates a target command from the output of the target model controller, based on the predetermined working coordinate system for each control axis and in accordance with a geometric relationship of a machine structure of the target device. The control device supplies the target command to the target device. This configuration can perform the model predictive control to supply a target command for causing the output of the target device to appropriately follow a predetermined command.