Differential Steering Control for CVT Machines
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Solution Overview
Problem
Conventional hydro-mechanical steering differential systems in track-type tractors face difficulties in maintaining a constant turning radius, especially at low speeds or high loads, leading to engine lugging and increased emissions when trying to achieve a commanded turn radius.
Innovation Solution
A steering control system incorporating a continuously variable transmission, a motor, and a control unit that adjusts the motor speed based on changes in transmission speed and engine load to maintain a desired turn radius, utilizing a steering device to provide directional input and sensors for real-time feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If operator steering lever or mechanism is used for turning control, then the machine can be steered in left or right directions, but it is difficult to maintain a constant turning radius especially at low speeds or high loads
Solution Approach 1:
The control unit continuously monitors the actual turn radius through sensors and compares it with the desired turn radius, then dynamically adjusts the steering motor speed to maintain the commanded turn radius. This closed-loop feedback system eliminates the difficulty of maintaining constant turning radius at low speeds or high loads.
Solution Approach 2:
The system dynamically adjusts the steering motor speed based on real-time operating conditions (speed and load) to maintain the desired turn radius. Instead of fixed mechanical steering ratios, the system adapts the steering response dynamically, allowing precise turn radius control across varying operating conditions.
2Measurement precision
If transmission ratio is reduced to achieve commanded turn radius when steering motor reaches maximum displacement, then the desired turn radius can be achieved, but the engine may lug and emissions increase
Solution Approach 1:
The control unit changes the operating parameters of the steering motor (speed and displacement) dynamically based on engine load and vehicle speed conditions. By adjusting the steering motor speed rather than reducing transmission ratio, the system achieves the desired turn radius without forcing the engine into lugging conditions, thereby reducing emissions.
Solution Approach 2:
The system dynamically adjusts steering motor speed based on real-time engine load conditions. When engine load is high, the system modifies the steering motor speed profile to achieve the commanded turn radius without reducing transmission ratio, preventing engine lugging and associated harmful emissions.
3Measurement precision
If steering motor operates at maximum speed to achieve tight turn radius, then the desired turn radius can be achieved, but vehicle speed must be reduced which affects productivity
Solution Approach 1:
The control unit dynamically changes the steering motor speed parameter based on the desired turn radius and current vehicle speed, rather than simply reducing vehicle speed. This allows the system to achieve tight turn radii through optimized steering motor control while maintaining higher vehicle speeds, thereby preserving productivity.
Data Source
AI summary
A differential steering control system and method for a machine includes a motor for steering the machine in a leftwards or a rightwards direction, a continuously variable transmission for moving the machine in a forwards or a backwards direction, and a control unit connected to the motor and the continuously variable transmission. The control unit determines the speed of the continuously variable transmission and based upon the determined speed, modifies a speed of the motor in order to achieve/maintain a desired turn radius for the machine.