Robot Force Control for Multi-Directional Sensor Overload
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Solution Overview
Problem
Existing robot control systems equipped with force sensors struggle to prevent excessive force components from exceeding the rated loads, leading to potential sensor failure, especially when operating with compact sensors or varying load conditions.
Innovation Solution
A robot control device with a comparing unit and controller that detects force components in multiple directions, compares them with predetermined threshold values, and adjusts the robot's operating speed or operation path to prevent excessive force, thereby maintaining the sensor's integrity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the robot operates at high speed with a force sensor, then productivity is improved, but the force sensor may exceed its rated load and fail
Solution Approach 1:
The control device calculates the estimated force component before the robot actually executes the motion, using the relationship between acceleration and force. By performing this estimation in advance during the planning phase, the system can identify potential overload conditions before they occur, allowing preventive action to be taken without affecting the robot's high-speed operation capability.
Solution Approach 2:
The invention dynamically adjusts the robot's operating speed based on the estimated force components. When the calculated force approaches the sensor's rated load, the control device automatically reduces the speed in that specific direction while maintaining high speed in other directions where the force is within limits. This dynamic speed adjustment preserves overall productivity while protecting the force sensor from overload.
2Reliability
If the robot reduces operating speed to prevent excessive force, then force sensor reliability is improved, but productivity decreases
Solution Approach 1:
The control device applies speed restriction selectively only in the specific direction where the estimated force component exceeds the threshold, while maintaining full operating speed in other directions where the force is within acceptable limits. This localized speed adjustment protects the force sensor from overload in critical directions without unnecessarily reducing productivity in non-critical directions.
Solution Approach 2:
The system changes the operating parameters (speed) dynamically based on the calculated force components. By continuously monitoring the relationship between acceleration commands and resulting force estimates, the control device adjusts speed parameters in real-time to keep force components within the sensor's rated load while maximizing overall productivity.
3Device complexity
If the robot uses a compact force sensor with lower rated load, then device complexity is reduced, but the robot must operate at lower speeds to prevent sensor failure
Solution Approach 1:
By calculating estimated force components before execution, the system can accurately predict when a compact force sensor will approach its lower rated load limit. This preliminary calculation allows the control device to plan motion trajectories and speed profiles that fully utilize the compact sensor's capabilities without overload, thereby maintaining high productivity despite using a smaller sensor.
Solution Approach 2:
The dynamic speed adjustment mechanism allows the robot to operate at high speeds when the compact force sensor is within its safe operating range, and automatically reduce speed only when necessary to prevent overload. This dynamic approach maximizes the utilization of the compact sensor's capacity while preventing failure, thereby maintaining high overall productivity despite the sensor's lower rated load.
Data Source
AI summary
A control device for a robot includes a comparing unit and a controller. When the robot equipped with a force sensor capable of detecting force components of a same type in a plurality of directions operates, the comparing unit compares a magnitude of each of the force components detected by the force sensor with a predetermined threshold value for each of the directions. If the comparing unit determines that a magnitude of a force component in any of the directions exceeds the threshold value, the controller controls the robot to avoid an increase in the magnitude of the force component in the direction.