Output speed control for hydro-mechanical continuously variable transmission of tractor.

Area of Science:

• Agricultural Engineering
• Control Systems Engineering
• Mechanical Engineering

Background:

• Tractor speed instability during field operations impacts efficiency and performance.
• Hydro-mechanical continuously variable transmissions (HMCVTs) are crucial for optimizing tractor operation.
• Existing HMCVT control strategies require enhancement for superior speed regulation.

Purpose of the Study:

• To develop and validate a comprehensive control strategy for improving HMCVT output speed stability in tractors.
• To analyze the speed, torque, and power diversion characteristics of HMCVT systems.
• To mitigate output speed fluctuations caused by various operational factors.

Main Methods:

• Analysis of HMCVT speed regulation, torque, and power diversion characteristics.
• Development of a hybrid control strategy combining engine speed control (fuzzy logic) and hydraulic displacement ratio control (feedforward and model predictive control).
• Validation through a joint simulation model under tractor acceleration and step load disturbance scenarios.

Main Results:

• The proposed control strategy effectively reduces engine speed fluctuation rate and impact.
• It significantly shortens the adjustment time for output speed stabilization.
• Demonstrated improvement in the overall operating speed stability of tractors equipped with HMCVT.

Conclusions:

• The integrated control strategy offers a robust solution for enhancing HMCVT performance in agricultural machinery.
• Fuzzy logic, feedforward compensation, and model predictive control synergistically improve tractor speed stability.
• This research contributes to more efficient and reliable tractor field operations through advanced HMCVT control.