Servo-Elastic Actuator Layout for Simultaneous Force and Position Control
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Solution Overview
Problem
Existing work piece processing devices face challenges in simultaneously achieving precise force and position control, especially when dealing with non-compliant surfaces, as servo-actuators struggle to control force accurately while maintaining position precision.
Innovation Solution
The integration of a compliance elastic member and a weight compensation elastic member between the servo-actuator and the work piece or frame, coupled with a controller that uses position and force sensors to adjust the servo-actuator's movement, allows for precise force control while maintaining accurate position control by modifying the force-to-position sensitivity ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a servo-actuator is used to control position accurately, then position control precision is improved, but force control precision deteriorates when pushing against a non-compliant surface
Solution Approach 1:
A compliant member is introduced as an intermediary element between the servo-actuator and the workpiece. This compliant member deforms under load, converting force changes into position changes that the servo-actuator can detect and control. The compliant member acts as a mediator that translates force information into position feedback, enabling the servo-actuator to indirectly control force through its high-precision position sensing capabilities.
Solution Approach 2:
The system changes the mechanical parameter of the actuator system by introducing compliance (柔度) through the compliant member. This transforms the rigid connection into a flexible one, allowing the system to convert force variations into measurable position variations. The compliant member's deformation characteristic (parameter) enables the servo-actuator to sense force changes through position measurement, resolving the force control precision issue.
2Force
If a long travel spring is used with a servo-actuator to control force precisely, then force control precision is improved, but position control capability is lost
Solution Approach 1:
Instead of using a long travel spring with large deformation, the invention uses a compliant member with optimized compliance parameters. The compliant member is designed with appropriate stiffness characteristics that allow sufficient deformation for force sensing while maintaining enough mechanical coupling to enable position control. This parameter optimization resolves the contradiction between force control precision and position control capability.
3Device complexity
If the compliant member can only be in compression, then structural simplicity is improved, but the system cannot distinguish forces below the weight load of the tool horn and carriage
Solution Approach 1:
A weight compensation elastic member is introduced to counterbalance the gravitational force acting on the tool horn and carriage. This elastic member is pre-loaded to generate an upward elastic force that offsets the weight of the moving components. By compensating for the weight load, the system can now detect and control forces below the original weight threshold, as the weight compensation elastic member effectively removes the gravitational offset from the force measurement range.
Solution Approach 2:
The weight compensation elastic member acts as an intermediary that introduces an opposing elastic force to counterbalance gravity. This intermediary element enables the compression-only compliant member to function over a broader force range by offsetting the gravitational baseline, allowing the system to measure and control both compressive and effectively tensile forces through the combined elastic forces.
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 configuration enables precise control of force and position simultaneously, allowing for accurate processing even when dealing with surfaces that are not fully compliant, and can control force down to zero, enhancing the accuracy and reliability of processes like ultrasonic welding and cutting.
Implementation Method 1
a compliance elastic member, such as a spring or elastomer, mechanically disposed with a servo-actuator in a force transmission path
Implementation Method 2
a weight compensation elastic member disposed so as to counterbalance a gravitational force acting on the tool device
Data Source
Figure 1A~3
Figure 4~9
Figure 5
AI summary
A work piece processing device includes a tool device, a work piece holder and a servo-elastic actuator system having simultaneous precision force and position control that moves one of the tool device and the work piece holder to the other of the tool device and work piece holder. The servo-actuator system including a servo-actuator, a compliance elastic member and a weight compensation elastic member disposed in a force transmission path with the compliance elastic member and the weight compensation elastic member disposed with respect to each other so that a spring force exerted by the weight compensation elastic member is opposed to a spring force exerted by the compliance elastic member.