Link Actuation Device Constant Speed Control
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Solution Overview
Problem
Link actuation devices with quadric chain link mechanisms face issues with uneven movement speed when changing posture, leading to working, coating, or welding unevenness due to non-constant arm rotation angles, especially when large changes in posture are required.
Innovation Solution
A control device that divides the trajectory into sections and calculates constant rotation speeds for each arm to maintain a target moving speed, ensuring the end effector operates at a substantially constant speed by setting rotation speeds for each section without acceleration or deceleration, using a divided section setter, arm rotation speed calculator, and posture change controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If uniform motion control is performed in synchronization by simply performing point-to-point control from posture A to posture B, then the control method is simple, but the arm rotation angles become greatly different from the theoretical values near intermediate portions of the trajectory, causing interference among arms and requiring excessive torque
Solution Approach 1:
The trajectory between posture A and posture B is divided into multiple sections (first section from A to intermediate posture C, second section from C to B). This segmentation allows different control strategies to be applied to different portions of the motion, improving overall accuracy while maintaining operational simplicity.
Solution Approach 2:
The intermediate posture C is determined in advance based on the start posture A and end posture B. By pre-calculating the intermediate position and dividing the trajectory accordingly, the system can prepare appropriate control parameters for each section before execution, avoiding real-time calculation complexities.
2Reliability
If the trajectory is divided into sections and point-to-point control is performed for each divided section to make change in posture, then excessive loads are avoided, but the end effector moves at uneven speed resulting in working, coating, or welding unevenness
Solution Approach 1:
The control method dynamically adjusts the motion parameters for each section based on the specific trajectory requirements. By calculating appropriate motion profiles for each divided section, the system maintains relatively uniform end effector speed while avoiding excessive loads, thus achieving both reliable operation and work uniformity.
Solution Approach 2:
The system changes motion parameters (such as speed, acceleration) for each section of the divided trajectory. By adjusting these parameters appropriately in different sections, the end effector maintains relatively uniform speed across the entire trajectory, preventing working, coating, or welding unevenness while managing device loads.
3Adaptability or versatility
If large changes in posture are required, then the operational range is wide, but the arm rotation angles deviate significantly from theoretical values causing interference and excessive torque requirements
Solution Approach 1:
Large posture changes are divided into multiple smaller sections with intermediate postures. This segmentation reduces the angular deviation in each section, preventing arm interference and excessive torque requirements while maintaining the ability to achieve large overall posture changes, thus preserving operational range without sacrificing control precision.
Data Source
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AI summary
In this link actuation device (1), arms (11a-13a) of a plurality of link mechanisms (11-13) are driven to be rotated by actuators (3), whereby the posture of a distal end side link hub (15) is changed. A divided section setter (42) divides a trajectory on a work surface (60) on which an end effector (8) works, into a plurality of sections at pass points and sets the sections. An arm rotation speed calculator (43) calculates a rotation speed at which each arm performs constant speed rotation in each section on the basis of: a time period of movement in the section which is determined from a target moving speed and the distance of the section; and a rotation-angular movement amount of the arm in the section. A posture change controller (41) performs positioning control on each actuator (3) so as to cause its corresponding arm to continuously rotate at the corresponding rotation speed without acceleration/deceleration.