Robot Joint Control Modes for Fast Motion and Precise Positioning
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Solution Overview
Problem
Manipulators in production lines face challenges with backlash in reduction gears, leading to vibration and positioning errors, requiring high positioning accuracy and compliance depending on operational conditions.
Innovation Solution
A robot system with two driving sources and a control device that executes different processes based on motion requirements, using a transmission mechanism with reduction gears to manage torque and rotation direction, allowing for high-speed movement and precise positioning while minimizing vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full-closed loop control is used with encoder on output side of reduction gears, then positioning accuracy is improved, but moving speed decreases
Solution Approach 1:
The system dynamically switches between two control modes: full-closed loop control for high positioning accuracy and semi-closed loop control for high moving speed. The control device selects the appropriate control mode based on the operational requirements, allowing the manipulator to adapt its control characteristics in real-time.
Solution Approach 2:
The invention changes the control parameter configuration by using two different control loops with different encoder placements. The full-closed loop control uses an encoder on the output side of reduction gears for high precision, while the semi-closed loop control uses an encoder on the motor shaft for high speed movement.
2Power
If high-power torque is applied to move manipulator, then moving capability is improved, but vibration increases
Solution Approach 1:
The control device applies preliminary anti-action by detecting the direction of movement and applying pre-tension torque in the same direction before actual movement occurs. This prevents backlash in the reduction gears and eliminates vibration caused by gear engagement, allowing high-power torque to be applied without generating harmful vibrations.
Solution Approach 2:
The system performs preliminary action by advancing the manipulator slightly beyond the commanded position in the movement direction, then using feedback control to return to the exact target position. This preliminary overshoot ensures that the manipulator moves through the backlash zone before precision positioning is required.
3Ease of operation
If compliance is increased to ease component insertion, then ease of operation is improved, but positioning accuracy decreases
Solution Approach 1:
The system dynamically adjusts compliance characteristics by switching between control modes. During insertion operations, the control device enables compliance control to ease component insertion. Once insertion is complete, the system switches to high-precision positioning mode to achieve accurate placement, thus adapting compliance levels to operational needs.
Data Source
AI summary
A robot includes a first driving source, a second driving source, an output portion to which both rotation of the first driving source and rotation of the second driving source are transmitted, and a control device configured to execute a first process and a second process. In the first process, the control device controls the first driving source and the second driving source such that when the output portion is rotated toward a predetermined direction, a rotational direction of the output portion is limited to the predetermined direction. In the second process, the control device controls the first driving source and the second driving source such that when the output portion is rotated toward a predetermined direction, the output portion is able to rotate toward a direction opposite to the predetermined direction.