Robotic Arm Backlash Error Compensation via Visual Sensor Feedback
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Solution Overview
Problem
Existing robotic arm systems face accuracy issues during assembly operations due to hysteresis errors caused by backlash in rotary joints, which affect the precise positioning and orientation of gripped objects relative to attachment targets.
Innovation Solution
A method for controlling a robotic arm that involves measuring the position and orientation of a gripped object using a visual sensor, determining a measurement teaching point to set the driving direction of joints to a definite direction, and correcting the object's position and orientation accordingly, thereby minimizing the impact of backlash errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If robot control data is generated or corrected based on relative positions and orientations detected by a visual sensor, then assembly accuracy is improved, but hysteresis errors occur due to backlash in rotary joints when rotational driving direction is reversed
Solution Approach 1:
The patent applies preliminary action by determining the driving direction of each rotary joint in advance before generating or correcting robot control data. The system calculates the driving direction from the current teaching point to the measurement teaching point and from the measurement teaching point to the attachment teaching point, ensuring that the joint rotates in a definite direction without reversal. This prevents backlash-induced hysteresis errors and maintains control accuracy throughout the assembly operation.
Solution Approach 2:
The patent changes the parameter of driving direction from variable (potentially reversing) to fixed (definite direction). By determining and constraining the driving direction of each rotary joint to be consistent throughout the movement from the current teaching point through the measurement teaching point to the attachment teaching point, the system eliminates hysteresis errors caused by directional reversals while maintaining the benefits of visual sensor-based correction.
2Measurement precision
If the robotic arm is controlled to move to correct positions and orientations based on sensor detection, then positioning precision is improved, but backlash in decelerators causes hysteresis errors when rotational direction changes
Solution Approach 1:
The system performs preliminary determination of the driving direction for each rotary joint before executing the positioning correction. By calculating the required rotation direction from the current teaching point to the measurement teaching point and from the measurement teaching point to the attachment teaching point in advance, the system ensures continuous rotation in a definite direction, preventing backlash-induced hysteresis and maintaining control precision.
Solution Approach 2:
The patent uses visual sensor feedback to detect the actual positions and orientations of the gripped object and attachment target, then generates or corrects robot control data based on this feedback. The system incorporates feedback about the driving direction of rotary joints to ensure that corrections are applied without causing directional reversals, thereby eliminating hysteresis errors while maintaining the precision benefits of sensor-based feedback control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables high-accuracy control of the robotic arm during assembly operations by ensuring that the driving direction of all rotary joints remains consistent, reducing the adverse effects of backlash and improving the precision of position-orientation control.
Implementation Method 1
measuring a position or an orientation of a gripped object gripped with a gripping device of a robotic arm by using a measurement device
Data Source
AI summary
A robot apparatus includes: a robotic arm provided with a robotic hand capable of changing its position and its orientation by using joints; a visual sensor which measures a position or an orientation of a gripped object gripped with the robotic hand at a measurement teaching point; and a control device. The control device controls the position or the orientation of the gripped object when the gripped object is attached to an attachment target object at a corrected teaching point corrected based on a measurement result by the visual sensor. In this case, the control device determines a measurement teaching point, where the measurement with the visual sensor takes place, such that a driving direction of each of the joints from the measurement teaching point to the corrected teaching point is set to a definite driving direction.