Axial Piston Pump Trajectory Planning Under System Constraints
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Solution Overview
Problem
Hydraulic systems face challenges in real-time control due to physical and geometric limitations, leading to suboptimal or unrealizable trajectories when using flatness-based pilot control, and require numerical optimization in model predictive control, which is computationally expensive and resource-intensive.
Innovation Solution
An extended state variable filter is used to generate a setpoint trajectory that adheres to manipulated variable and state variable limitations, allowing for real-time trajectory planning without numerical optimization, by dynamically limiting derivatives and prioritizing constraints, ensuring feasibility and adherence to system limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If model predictive control (MPC) is used to systematically consider constraints in control system, then constraint satisfaction is improved, but computational cost and hardware requirements increase
Solution Approach 1:
The patent extracts the constraint satisfaction function from the complex MPC optimization process and implements it through a simplified extended state variable filter that directly enforces constraints on the trajectory and its derivatives without requiring numerical optimization at runtime
Solution Approach 2:
The patent replaces the numerical optimization mechanism of MPC with an analytical filtering approach that uses differential equations and derivative limiting to achieve the same constraint satisfaction goal with significantly reduced computational burden
2Speed
If flatness-based feedforward control with state variable filter is used for real-time control, then real-time capability is improved, but constraint satisfaction deteriorates
Solution Approach 1:
The patent makes the state variable filter dynamic by extending it to consider not only the trajectory itself but also its derivatives up to order n, allowing the filter to adaptively adjust the trajectory to satisfy constraints while maintaining real-time performance
Solution Approach 2:
The patent performs preliminary constraint satisfaction by limiting the derivatives of the setpoint trajectory before they are applied to the system, ensuring that constraints are met in advance rather than requiring corrective action during execution
3Ease of manufacture
If conventional trajectory planning is used without considering system limitations, then trajectory generation simplicity is improved, but trajectory feasibility deteriorates
Solution Approach 1:
The patent changes the parameters of the trajectory planning by incorporating derivative limits and constraint orders into the extended state variable filter, transforming a simple trajectory generator into one that systematically ensures feasibility while maintaining relative simplicity
Data Source
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AI summary
The invention relates to a method for producing, for a hydraulic machine having an actuator, a setpoint-value trajectory (∆p p plan ) satisfying predefined limitations in order to influence an output variable (∆pp) of the hydraulic machine (100), wherein: a trajectory of unlimited setpoint values (∆p p des ) is fed to a trajectory planning means (210), which produces the setpoint-value trajectory (∆p p plan ) from the trajectory of unlimited setpoint values (∆p p des ); in the trajectory planning means (210), the trajectory of unlimited setpoint values (∆ppdes) is differentiated at least twice in order to obtain a trajectory (z ̈ ref ) of unlimited setpoint values that is differentiated n times; in the trajectory planning means (210), at least one limitation (212, 213, 214) is applied to the differentiated trajectory (z ̈ ref ) of unlimited setpoint values in order to obtain a differentiated trajectory (γ Lim) of limited setpoint values, and the differentiated trajectory (γ Lim) of limited setpoint values is fed to a filter integrator chain (215) in order to obtain the setpoint-value trajectory (∆p p plan ).