Vehicular Pump Displacement Control for Uniform Engine Speed
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Solution Overview
Problem
Existing vehicle systems with hydrostatic transmissions experience uncomfortable driving sensations and decreased performance due to varying engine speeds based on load conditions during forward and rearward motion, relying on a single predetermined mapping.
Innovation Solution
Implementing a control unit that switches between two distinct control laws for pump displacement based on forward or rearward motion, adjusting engine speed uniformly across different load conditions using a switching device and transducer feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single predetermined mapping is used to control pump displacement as a function of engine speed, then the control system remains simple, but the vehicle exhibits different engine speeds during forward and rearward motion causing driver discomfort and performance decrease
Solution Approach 1:
The control system is segmented into two distinct control laws: a first control law for forward motion and a second control law for rearward motion. This segmentation allows each control law to be optimized independently for its specific direction, eliminating the engine speed variations that cause driver discomfort while maintaining overall system manageability through dedicated control strategies for each motion direction.
2Productivity
If a single predetermined mapping is used for pump displacement control, then the system structure remains simple, but vehicle performance and efficiency decrease due to varying engine speeds under different load conditions
Solution Approach 1:
The control system transitions from a static single mapping approach to a dynamic dual control law structure that adapts based on motion direction. The control unit selectively applies the first control law during forward motion and the second control law during rearward motion, enabling the system to optimize pump displacement dynamically for each direction's specific load characteristics, thereby improving vehicle performance and efficiency.
3Adaptability or versatility
If engine speed varies based on load conditions during starting, then the pump displacement can adapt to load, but the vehicle starts with different engine speeds depending on direction causing uncomfortable driver sensation
Solution Approach 1:
The control system applies local quality by implementing direction-specific control characteristics tailored to each motion direction's load profile. The first control law is optimized for forward motion load characteristics while the second control law is optimized for rearward motion load characteristics, allowing each direction to adapt locally to its specific conditions while maintaining consistent and comfortable engine speed behavior for the driver.
Data Source
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AI summary
A method for controlling the displacement of a pump (PM) mounted on a vehicle (VH) and driven by an engine (ICE) of the vehicle (VH), the method comprising the steps of determining if the vehicle (VH) is moving forward or rearward, setting a first control law for controlling said displacement when the vehicle (VH) moves forward, and setting a second control law for controlling said displacement when the vehicle (VH) moves rearward, wherein the first and the second control law are differently set such that a speed of the engine (ICE) variates as a function of a load parameter in the same manner when the vehicle (VH) moves forward and rearward, with the load parameter being indicative of a load acting on the vehicle (VH)