Force Compliant Coupling for Hydraulic Actuator Transient Reduction
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Solution Overview
Problem
Force control systems face inaccuracies in force application due to motion-induced errors, lack of symmetry, and instability, particularly when dealing with dynamic loads and force transients, which are not effectively addressed by existing methods that often compromise stability or increase system complexity.
Innovation Solution
A force compliant mechanism incorporating a volute spring member and real-time compensation algorithms for velocity and pressure, which decouples the test object from the actuator, reduces force transients and enhances stability by allowing accurate force control without integral compensation, using feedforward and feedback configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If classical control methods are used with hydraulic actuators and servo valves, then the system is simple to implement, but force control accuracy is unacceptable at maximum rated pressures and flows
Solution Approach 1:
The patent replaces the mechanical linkage between actuator and test object with a fluid coupling system. The actuator applies force to a fluid medium rather than directly to the test object, allowing force transmission without rigid mechanical connection. This substitution enables accurate force control at high pressures by decoupling the actuator's mechanical motion from the test object's motion requirements.
Solution Approach 2:
The patent introduces a fluid medium as an intermediary between the hydraulic actuator and the test object. This intermediary allows the actuator to apply force accurately while the test object can move independently according to its own dynamics. The fluid coupling acts as a mediator that transmits force without imposing motion constraints.
2Ease of operation
If the actuator is rigidly coupled to the test object, then the force application is direct, but the actuator restricts the motion of the test object and imposes uncharacteristical forces
Solution Approach 1:
The fluid medium serves as an intermediary that decouples the actuator from the test object, allowing the test object to move freely according to its natural dynamics while the actuator applies the desired force through the fluid coupling. This eliminates uncharacteristical forces that would arise from rigid mechanical constraints.
Solution Approach 2:
The patent changes the coupling parameter from rigid mechanical connection to fluid-based compliant connection. This parameter change allows the system to transition from imposing motion constraints to allowing natural motion while maintaining force control fidelity through the fluid's pressure-transmission properties.
3Measurement precision
If error integration is used to reduce steady state error, then static accuracy improves, but instability occurs during transitions in force polarity and settling time increases
Solution Approach 1:
The patent replaces the integral control mechanism with a fluid coupling system that naturally accommodates steady-state errors without causing instability. The fluid medium's compressibility and pressure-equilibrium properties provide inherent error compensation that avoids the oscillatory behavior and settling time issues associated with mathematical integration in dynamic systems.
4Measurement precision
If the actuator follows the motion of the test object, then motion restriction is minimized, but force control accuracy deteriorates due to motion-induced errors
Solution Approach 1:
The fluid medium acts as an intermediary that allows the actuator to apply force accurately while the test object moves at full speed according to its natural dynamics. The fluid coupling transmits force without requiring the actuator to follow or restrict the test object's motion, eliminating motion-induced force errors.
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
The solution significantly reduces force transients and improves stability, enabling accurate and efficient force control with reduced errors and quicker cycling of test objects, even under dynamic conditions.
Implementation Method 1
A force compliant volute spring member that has an input end and an output end is disposed within the housing
Data Source
Figure 1~3
Figure 2
Figure 4~8
AI summary
A force compliant mechanism (750) for a force control system (600) includes a housing (752). A force compliant volute spring member (754) that has an input end (790) and an output end (792) is disposed within the housing (752). A force actuator input shaft (798) operates in response to a force induced thereon. An output shaft (800) is coupled to the output end (792) and to a test object (802). A force transducer (780) is in operative coupling with the force actuator input shaft (798) and generates a force signal in response to the induced force. A method of reducing force transients and increasing stability within a force control system (660) includes applying a force on a test object (666). A force actuator (669) is decoupled from the test object (666). The overall stiffness of the force control system is reduced and dynamic energy is absorbed via a force compliant member (662) coupled to the test object (666) and the force actuator (669).