Hydraulic Free-Piston Engine Control Signals
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Solution Overview
Problem
Current fluid power systems for mobile applications, such as excavators and wheel loaders, face inefficiencies due to the need for internal combustion engines and hydraulic pumps sized for maximum load, leading to throttling losses and delayed responses to load variations.
Innovation Solution
The implementation of hydraulic free-piston engines with independent pressure and flow rate control, utilizing a dynamic trajectory model to determine piston trajectories and servo valve positions, allowing for real-time adjustment of fuel injection and servo valve operation to achieve desired flow rates at any load pressure without throttling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an internal combustion engine and hydraulic pump are sized for maximum load, then the system can handle maximum pressure and flow rate requirements, but the system efficiency is compromised due to throttling losses when operating at partial load
Solution Approach 1:
The patent applies dynamics by making the pump displacement variable rather than fixed. The pump displacement is dynamically adjusted based on real-time load requirements through control signals that modify the pump's geometric parameters, allowing the system to match output to demand and eliminate throttling losses while maintaining maximum load capacity when needed
Solution Approach 2:
The patent changes the physical parameter of pump displacement from a fixed design parameter to a variable control parameter. By continuously adjusting the displacement parameter based on load conditions, the system optimizes efficiency across the entire operating range while preserving the capability to deliver maximum pressure and flow rate when required
2Adaptability or versatility
If a variable displacement pump driven by an ICE is used to adjust flow rate in real time, then the system can provide desired flow rate at any pressure, but both the pump and ICE have long response times to load variations generating significant delay
Solution Approach 1:
The patent segments the control function by separating the pump control from the engine control. The pump is equipped with an independent electronic control unit that can adjust pump displacement rapidly without waiting for engine response, creating a fast-responding flow control mechanism that operates independently of the slower engine dynamics
Solution Approach 2:
The patent replaces the purely mechanical linkage between engine and pump with an electronic control system. Electronic control signals directly adjust pump displacement based on sensor feedback, eliminating the mechanical inertia and delay inherent in mechanical linkages while maintaining the ability to provide full flow rate adjustment range
3Loss of time
If a fixed displacement pump driven by an electric motor is used with frequency control, then the system can achieve short response times, but the nature of electric motors makes them inappropriate for mobile applications
Solution Approach 1:
The patent merges the advantages of electric motor control (fast response, electronic precision) with the advantages of diesel engine power (high power density, mobility). The diesel engine provides the necessary power for mobile applications while the electronic pump control system provides fast response time, combining the best of both power sources into a unified system
Data Source
AI summary
The subject matter of this specification can be embodied in, among other things, a method for operating a hydraulic free piston engine includes receiving, at an engine controller for a hydraulic free piston engine, an energy parameter that is representative of an amount of fluid energy to be output by the engine, and a measured fluid pressure value of a fluid load of the engine, determining a piston trajectory of a piston within a hydraulic chamber of the engine, determining a fuel volume value and a servo valve actuation parameter, based on the energy parameter and the measured fluid pressure value, providing a fuel control signal to a fuel control device of the engine based on the fuel volume value, and providing, based on the servo valve actuation parameter and the piston trajectory, a servo valve control signal to a servo valve.