Hybrid MDPS EHPS Steering System Torque Fluctuation Control
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Solution Overview
Problem
Commercial vehicles require higher steering capacity than passenger vehicles, and existing Motor Driven Power Steering (MDPS) and Electro-Hydraulic Power Steering (EHPS) systems struggle to meet this need while maintaining fuel efficiency, often causing torque fluctuations that affect driver feedback and steering performance.
Innovation Solution
A hybrid motor driven power steering system combining a ball nut type gearbox with MDPS and EHPS units, controlled by a main steering device, and utilizing two torsion bars to stabilize torque fluctuations, along with an auxiliary EHPS unit to enhance steering capacity and fuel efficiency, particularly for medium-sized and full-sized vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If MDPS or EHPS device is used to improve fuel efficiency, then fuel efficiency is improved, but steering capacity is insufficient for commercial vehicles
Solution Approach 1:
The patent combines MDPS and EHPS devices into a hybrid system that integrates electric motor assistance with hydraulic power steering. This merging allows the system to achieve both fuel efficiency improvement (from electric motor) and sufficient steering capacity (from hydraulic assistance), resolving the contradiction between energy savings and steering force requirements for commercial vehicles.
Solution Approach 2:
The hybrid steering system serves multiple functions: it provides fuel efficiency improvement through electric motor assistance, delivers high steering capacity through hydraulic power, and adapts to different steering conditions. This multi-functionality allows a single system to meet both the fuel efficiency goals and the high steering capacity requirements of commercial vehicles.
2Force
If MDPS and EHPS devices are used together, then steering capacity is increased, but torque fluctuation occurs affecting driver feedback
Solution Approach 1:
The patent incorporates feedback mechanisms that monitor torque fluctuations in the hybrid steering system. By detecting torque variations and adjusting the control parameters of both MDPS and EHPS components, the system compensates for instability and ensures smooth torque delivery to the steering wheel, maintaining stable driver feedback while achieving high steering capacity.
Solution Approach 2:
The system dynamically adjusts control parameters of the MDPS and EHPS units based on operating conditions. By changing parameters such as motor torque, hydraulic pressure, and assist force distribution, the system optimizes torque stability and eliminates fluctuations that would otherwise affect driver feedback, while maintaining the required steering capacity.
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 system achieves a steering capacity of 50 KN to 190 KN, improves fuel efficiency, and ensures accurate reflection of road surface reactions, reducing torque fluctuations and enhancing driver feedback and overall steering performance.
Implementation Method 1
two torsion bars which are respectively installed at different positions of the steering column to detect a road surface reaction force which is introduced to the ball nut type gear box and transferred to the steering wheel
Implementation Method 2
a ball nut type gear box which is input with driver steering torque, motor output torque and hydraulic output torque to generate output torque to operate a tie rod
Data Source
AI summary
A hybrid motor driven power steering system for a commercial vehicle may include a MDPS unit to generate motor output torque depending on driver steering torque, an EHPS unit to generate hydraulic output torque considering the motor output torque of the MDPS unit, a ball nut type gear box to generate output torque which operates a tie rod leading to left and right wheels after being input with the driver steering torque, the motor output torque, and the hydraulic output torque, and two torsion bars to block torque fluctuation rates at respective regions of a joint by detecting a road surface reaction force transferred to a steering column through the ball nut type gear box in at least two different positions. Accordingly, it may be possible to provide a steering capacity required in small-sized, medium-sized and full-sized commercial vehicles.