Parallel Link Work Device Velocity Control
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Solution Overview
Problem
Work devices using parallel link mechanisms often operate abruptly at high velocities when changing the posture of an end effector, even if the work point is not moved or is moved only slightly, leading to potential motor overload and operational instability, especially when less-experienced operators are involved.
Innovation Solution
A work device with a parallel link mechanism that includes a control system with a switching function unit to automatically switch between work-point movement velocity and posture change velocity based on movement distance and velocity thresholds, preventing abrupt high-velocity operations by adjusting the target velocity for the actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the work point of the end effector is continuously moved at a constant velocity, then the productivity is improved, but the work device may operate abruptly at high velocity when only posture is changed, causing motor overload
Solution Approach 1:
The control device dynamically switches between two control modes: work-point movement velocity mode and posture change velocity mode. This dynamic adaptation allows the system to maintain constant velocity during productive movement while preventing abrupt high-velocity operations during posture changes, thus resolving the contradiction between productivity and motor protection.
Solution Approach 2:
The system changes the control parameter from work-point movement velocity to posture change velocity based on the operational state. By detecting whether the work point is moving or only the posture is changing, the control device adjusts the velocity parameter accordingly, preventing motor overload while maintaining efficiency during actual work movements.
2Loss of time
If the velocity of tip positions is commanded to shorten time, then the productivity is improved, but the entire work device starts abruptly operating at high velocity, affecting the motor
Solution Approach 1:
The control device dynamically adjusts the velocity command based on the operational mode. During work-point movement, it uses work-point movement velocity to minimize time. During posture changes, it switches to posture change velocity to prevent abrupt operations. This dynamic control resolves the contradiction between time efficiency and harmful abrupt movements.
Solution Approach 2:
The control device continuously monitors the operational state to determine whether the work point is moving or only the posture is changing. Based on this feedback, it automatically switches between appropriate velocity modes, preventing abrupt high-velocity operations while maintaining time efficiency during productive work movements.
3Ease of operation
If the control method is simplified for easier operation, then the ease of operation is improved, but the system cannot handle cases where only posture is changed without work point movement
Solution Approach 1:
The control device automatically detects whether the work point is moving or only the posture is changing, and self-adjusts the velocity mode accordingly. This self-service capability allows less-experienced operators to use the system without manual intervention, while still handling complex posture change scenarios, thus resolving the contradiction between ease of operation and adaptability.
Data Source
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AI summary
The parallel link mechanism is applied to a work device (1) in which a link actuation device (7) and a combined-side actuator (71) are combined. A control device (2) includes a storage (3) that stores a plurality of work coordinates as well as a work-point movement velocity as a target velocity of an end effector (6) and a posture change velocity as a target angular velocity to be set for changing the posture of the end effector (6). A controller (4) includes a switching function unit (4a) that switches the target velocity used for calculating movement velocities of the respective posture control actuators (11-1, 11-2, 11-3) and a movement velocity of the combined-side actuator (71), to the work-point movement velocity and to the posture change velocity.