Encoder-Based Robot Hand Gripping Force Control Without Pressure Sensors
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Solution Overview
Problem
Conventional robot hands face difficulties in gripping a variety of workpieces with appropriate force without damaging them, as they require manual adjustment of gripping force based on the workpiece's material, and the addition of pressure sensors increases manufacturing costs.
Innovation Solution
A robot hand with a motor-driven claw system, an encoder for rotational position detection, and a control device that limits torque, estimates contact through rotational position change, gradually increases torque, and maintains it based on movement limits to ensure appropriate gripping force without damaging workpieces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gripping force is increased to firmly grip hard workpieces, then the gripping reliability is improved, but soft workpieces may be damaged
Solution Approach 1:
The robot hand dynamically adjusts the gripping force in two stages: initially applying a limited torque to avoid damage, then increasing to a higher torque when contact is detected. This dynamic adjustment allows the same robot hand to safely grip both soft and hard workpieces without damage or slippage.
Solution Approach 2:
The system changes the torque parameter from a fixed value to a variable that can take two distinct values: a torque limit value for initial contact and a higher torque upper limit value for firm gripping. This parameter change enables adaptive gripping force adjustment based on workpiece hardness.
2Adaptability or versatility
If a pressure sensor is added to detect gripping force and adjust automatically, then the adaptability to various workpieces is improved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces the pressure sensor-based detection system with a motor torque control system. Instead of using additional sensors to detect gripping force, the system uses the motor's existing torque control capability combined with encoder feedback to achieve the same adaptability, thereby avoiding increased manufacturing costs.
Solution Approach 2:
The robot hand uses its own motor and encoder system to detect contact and adjust gripping force, rather than relying on external pressure sensors. The motor's torque characteristics and the encoder's position feedback work together to provide self-service detection and adjustment functionality.
3Object-affected harmful factors
If the gripping force is set to be weak to avoid damaging soft workpieces, then workpiece damage is prevented, but the workpiece may fall during gripping
Solution Approach 1:
The system dynamically transitions from a weak gripping force (torque limit value) to a strong gripping force (torque upper limit value) upon detecting workpiece contact. This ensures that soft workpieces are initially gripped gently to prevent damage, then firmly held to prevent falling.
4Manufacturing precision
If manual adjustment of gripping force is required for each workpiece type, then appropriate gripping force can be applied, but the operation complexity and time consumption increase
Solution Approach 1:
The robot hand automatically detects workpiece contact through the motor's rotational position feedback and self-adjusts the gripping force without manual intervention. The system autonomously transitions from torque limit to torque upper limit based on contact detection, eliminating the need for operators to manually adjust settings for different workpiece types.
Solution Approach 2:
The encoder provides feedback on the motor's rotational position, enabling the control device to detect when the claws have contacted the workpiece. This feedback mechanism allows automatic adjustment of gripping force without manual intervention, maintaining accuracy while reducing operation complexity.
Data Source
AI summary
A robot hand includes a motor, claws configured to grip a workpiece in accordance with rotation of the motor, an encoder configured to detect a rotational position of the motor, and a control device configured to control a torque of the motor such that the claws grip the workpiece in accordance with the rotational position.