Hydrostatic Transmission Controller for Operator-Selectable Drive Modes
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Solution Overview
Problem
Operators of machines equipped with hydrostatic transmission systems face challenges in controlling speed and torque due to unfamiliar response characteristics, which can lead to operator fatigue and difficulty in handling machines in rough terrain, especially for unskilled operators.
Innovation Solution
A drive system with a power source, transmission, and a controller that adjusts the operation of a traction device based on operator-selected transmission modes, allowing for customizable speed rate changes and mimicking the response of power-shift transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a hystat transmission system is used, then fuel efficiency and functionality are improved, but operator comfort and control ease deteriorate due to unfamiliar response characteristics
Solution Approach 1:
The system dynamically adjusts transmission control parameters based on operator input and machine operating conditions. The controller continuously modifies pump and motor displacements to achieve desired acceleration and deceleration rates, making the hystat system adaptable to operator expectations while maintaining fuel efficiency benefits.
Solution Approach 2:
The system changes key operational parameters such as acceleration rate, deceleration rate, and neutral coasting behavior to match operator preferences. By adjusting these parameters through controller intervention, the hystat transmission can provide familiar power-shift-like characteristics while retaining its inherent fuel efficiency advantages.
2Speed
If pump and motor displacements are immediately neutralized in a hystat system, then speed control responsiveness is improved, but operator control difficulty increases due to extended coasting or rapid stopping
Solution Approach 1:
The controller performs preliminary actions by gradually reducing pump and motor displacements before complete neutralization. This staged approach prevents sudden coasting or rapid stopping by preemptively adjusting displacements to match desired deceleration rates, thereby maintaining speed control responsiveness while improving operator control ease.
Solution Approach 2:
The system uses feedback from operator input devices and machine operating conditions to continuously adjust displacement reduction rates. The controller monitors actual speed changes and modifies pump/motor displacement adjustments accordingly, ensuring that speed control remains responsive while preventing excessive coasting or abrupt stopping that would difficulty operator control.
3Device complexity
If a single control mode is used in a hystat system, then system simplicity is maintained, but adaptability to varying conditions and operator skill levels deteriorates
Solution Approach 1:
The controller is designed to perform multiple control functions within a single integrated system. It can operate in different control modes (e.g., acceleration control, deceleration control, neutral coasting control) and adapt to various operating conditions and operator skill levels, providing universal adaptability without requiring separate control systems for each function.
Solution Approach 2:
The control system dynamically switches between different control strategies based on operating conditions and operator input. The controller can adjust its behavior to provide different acceleration and deceleration characteristics, making the system adaptable to varying terrain, load conditions, and operator preferences while maintaining a single unified control architecture.
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
Enhances operator comfort and control by allowing selection of transmission modes that match familiar power-shift systems, improving control and reducing operator fatigue across varying terrain and skill levels.
Implementation Method 1
a hydrostatic transmission (hystat) that pressurizes fluid with an engine-driven pump for powering a motor connected to the traction device
Implementation Method 2
A hystat provides an infinitely variable torque-to-speed output ratio within its overall range through the pairing of a variable displacement pump and a fixed- or variable-displacement motor
Data Source
AI summary
A drive system for a mobile machine is disclosed. The drive system includes a power source configured to generate mechanical power, and a transmission driven by the power source, a traction device driven by the transmission. The drive system further includes a first input device configured to generate a signal to operate the machine, a second input device configured to receive an operator selection of one of a plurality of transmission modes, and a controller in communication with the first input device and the transmission. The controller is configured to adjust operation of the transmission to control a speed rate of change of the traction device in response to the signal from the first input device and based on the operator-selected one of the plurality of transmission modes.