Hydraulic Work Vehicle Speed Control Under Variable Load
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Solution Overview
Problem
Existing work vehicle speed control systems face challenges in accurately maintaining target vehicle speeds due to variations in engine rotational speed and hydraulic pressure, leading to inefficiencies and potential stalling.
Innovation Solution
A feedback control system is implemented to adjust the pilot pressure of hydraulic pumps based on detected rotational speeds and differential pressures, using feedback gains that increase with lower target speeds or larger pressure differences to minimize speed discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is performed with fixed feedback gain, then control simplicity is maintained, but speed control accuracy deteriorates under varying load conditions
Solution Approach 1:
The feedback gain is made dynamic by adjusting it according to the detected rotational speed of the hydraulic motor. The control circuitry stores multiple feedback gain values and selects the appropriate gain based on the current rotational speed range, allowing the system to adapt to varying operating conditions and maintain accurate speed control without excessive complexity
Solution Approach 2:
The feedback gain parameter is changed based on the rotational speed detection results. The control circuitry divides the rotational speed range into multiple regions and assigns different feedback gain values to each region, optimizing control accuracy for different speed conditions while managing system complexity through structured parameter adjustment
2Measurement precision
If feedback gain is increased to improve response at low speeds, then low-speed control accuracy improves, but high-speed stability deteriorates
Solution Approach 1:
The feedback gain is dynamically adjusted based on the detected rotational speed range. Higher feedback gains are applied when the hydraulic motor operates at low speeds to improve response and accuracy, while lower feedback gains are used at high speeds to maintain stability, preventing oscillations and ensuring smooth operation across the entire speed range
Solution Approach 2:
Different feedback gain values are applied to different rotational speed regions. The control circuitry detects the current speed and selects the appropriate gain from stored values optimized for that specific speed range, ensuring locally optimal control characteristics for each operating condition rather than using a single global gain value
3Reliability
If pilot pressure is increased to maintain target speed under heavy load, then speed maintenance improves, but energy consumption increases
Solution Approach 1:
The control system continuously detects the actual rotational speed of the hydraulic motor and compares it with the target speed. Based on this feedback, the control circuitry adjusts the pilot pressure to the variable displacement pump to minimize speed deviation, ensuring reliable speed maintenance under varying loads while optimizing energy consumption by applying only the necessary pressure correction
Solution Approach 2:
The feedback control system automatically adjusts the pilot pressure in response to speed deviations caused by load variations. The control circuitry monitors speed and independently manages the pump pressure without external intervention, maintaining target speed reliability while minimizing unnecessary energy consumption through adaptive pressure regulation
Data Source
AI summary
A speed control method for a work vehicle, includes driving an engine to rotate a first hydraulic pump provided in the work vehicle. Hydraulic fluid from the first hydraulic pump is supplied to a first hydraulic motor to rotate the first hydraulic motor to drive a first traveling device provided in a vehicle body of the work vehicle. A rotational speed of the first hydraulic motor is detected. Feedback control with respect to the engine and a control valve configured to control a pilot pressure of the first hydraulic pump is performed. The feedback control being performed to reduce a speed difference between the rotational speed detected and a target rotational speed of the first hydraulic motor corresponding to a target vehicle speed. A feedback gain of the feedback control is set based on a first coefficient which becomes larger as the target rotational speed becomes lower.