Hydrostatic Drive Clutch Control for Smooth Motor Engagement
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Solution Overview
Problem
Existing hydrostatic drive systems in mobile work machines engage hydraulic motors at high speeds, leading to noticeable and audible synchronization torque, and do not ensure necessary engagement only when required, limiting efficiency and comfort.
Innovation Solution
A method for controlling a hydrostatic drive system with multiple hydraulic machines, using a control unit to detect travel commands, calculate threshold speeds for clutch engagement, and adjust based on current deceleration and switching time, ensuring engagement only when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the second hydraulic motor is engaged at high speeds to achieve higher travel speeds, then the travel speed range is improved, but synchronization torque becomes noticeable and audible, reducing comfort
Solution Approach 1:
The control unit calculates a threshold value for clutch engagement based on the travel command before engagement occurs. By determining the appropriate engagement point in advance using predicted threshold calculations, the system ensures engagement happens at optimal speeds that avoid audible synchronization torque while achieving the desired travel speed range.
Solution Approach 2:
The control unit continuously monitors the actual travel speed and compares it with the target speed from the travel command. Based on this feedback, the control unit adjusts the clutch engagement timing and threshold values dynamically, ensuring engagement occurs only when necessary and at speeds that minimize audible synchronization torque.
2Device complexity
If the clutch is engaged based on simple accelerator pedal-dependent shift speeds, then the control strategy is simple, but engagement occurs at high speeds when not necessary, reducing efficiency and comfort
Solution Approach 1:
The control unit calculates threshold values for clutch engagement in advance based on the travel command and system state. This preliminary calculation allows the system to determine the optimal engagement point before it is reached, avoiding unnecessary engagements at high speeds while maintaining a relatively simple control structure.
Solution Approach 2:
The control unit uses feedback from the actual travel speed and travel command to dynamically adjust engagement decisions. By continuously monitoring system state and comparing actual speed with target speed, the system engages the clutch only when necessary and at appropriate speeds, eliminating wasteful engagements while keeping the control strategy manageable.
3Device complexity
If the threshold value for clutch engagement is fixed, then the control logic is simple, but it does not account for current deceleration and switching time, leading to suboptimal engagement timing
Solution Approach 1:
The threshold value for clutch engagement is made dynamic rather than fixed. The control unit continuously adapts the threshold based on the current travel command and system state, allowing the engagement timing to respond to changing operating conditions such as deceleration and switching time requirements.
Solution Approach 2:
The control unit uses feedback from the current travel state and travel command to continuously update the threshold value. This feedback mechanism ensures that engagement timing accounts for current deceleration and switching time, optimizing the engagement moment without requiring excessively complex control logic.
Data Source
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AI summary
The present invention relates to a method for controlling a hydrostatic drive (1) of a mobile working machine, wherein the hydrostatic drive is provided with a first hydraulic machine (4) with adjustable displacement volume and with a second hydraulic machine (6) and a third hydraulic machine (8), each with adjustable displacement volume, wherein the second hydraulic machine (6) is rotatably connected to the at least one driven wheel or chain or axle by means of a coupling (38), wherein the third hydraulic machine (8) is rotatably connected to the at least one driven wheel or chain or axle, wherein the coupling is controlled as a function of a travel speed of the mobile working machine, wherein the method comprises the following steps: a. detecting a travel command corresponding to a target travel speed or a value dependent thereon; b.Calculation of a threshold value for the travel speed of the working machine at which a switching of the clutch (38) is to take place; c. Whereupon, in the event that the travel command corresponds to an absolute value of the target travel speed of the working machine which is less than a specified value, the threshold value calculated in step b. is further adjusted taking into account an actual deceleration of the working machine and a switching time.