Hydrostatic Drive Torque-Speed Control Under Power Limits
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Solution Overview
Problem
Existing hydrostatic drive systems for mobile machinery lack the ability to seamlessly transition between torque-based and speed-based driving modes without requiring a mode switch, and they cannot directly control power consumption, necessitating indirect methods that lead to inefficiencies.
Innovation Solution
A method for controlling hydrostatic drives by alternately targeting output torque or output speed, incorporating power limitations, which involves calculating target pressures or swashplate angles based on hydraulic pump displacement volumes, and using pressure regulators to manage power within the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque-based driving control is implemented, then output torque control precision is improved, but power consumption cannot be directly controlled and must be achieved indirectly through angular limitations
Solution Approach 1:
The system dynamically changes control parameters by switching between torque-based mode (using target output torque) and speed-based mode (using target output speed) depending on operating conditions. This allows direct power consumption control in speed-based mode while maintaining torque control precision when needed, resolving the contradiction through parameter adaptation.
2Use of energy by moving object
If speed-based driving control is implemented, then power consumption can be directly controlled, but seamless transition to torque-based driving requires mode switching which complicates the control system
Solution Approach 1:
The control system is designed with multi-functionality to handle both torque-based and speed-based driving modes within a single unified framework. The control unit can seamlessly switch between control strategies based on operating conditions, eliminating the need for separate mode switches and reducing overall system complexity while maintaining both control capabilities.
3Use of energy by moving object
If power limitation is implemented in hydrostatic drives, then power consumption is reduced, but the ability to achieve target speed or torque is compromised
Solution Approach 1:
The system dynamically adapts control parameters based on power limitation conditions. When power limits are reached, the control unit automatically adjusts between torque-based and speed-based control modes, modifying control targets and parameters in real-time to ensure reliable achievement of operational goals while respecting power constraints.
Solution Approach 2:
The control system incorporates feedback mechanisms that continuously monitor power consumption, output torque, and speed. Based on this feedback, the control unit determines when power limitations are active and adjusts control parameters accordingly, ensuring that target speed or torque is reliably achieved within available power constraints through iterative optimization.
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
Enables smooth transitions between torque-based and speed-based driving without mode switches, directly controlling power consumption to enhance efficiency and reduce power limitations.
Implementation Method 1
the pressure and volume flow generated by the hydraulic pump can be controlled by influencing a control pressure
Implementation Method 2
processing the data from step b. Calculated target pressure, taking into account the maximum input power, if the hydrostatic drive is to be controlled by means of a target output torque; calculation of a maximum pressure that may be generated by the hydraulic pump
Data Source
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AI summary
The present invention relates to a method for limiting the power output of a hydrostatic drive (1), the method comprising the following steps: a. Receiving the command to control the hydrostatic drive (1) by means of a target output torque (TDrv) or a target output speed (nsoll); b. Calculating a target pressure (Δpdes) generated by the hydraulic pump (4) that can provide the desired target output torque (TDrv), taking into account a displacement volume of the hydraulic motor (6, 8), or calculating a target swivel angle (αdes) of the hydraulic pump (4) that can provide the desired target output speed (nsoll), taking into account the displacement volume of the hydraulic motor (6, 8); c. Obtaining information about a maximum input power (Pm) of the hydraulic pump (4); d. Processing the data from step b.calculated target pressure (Δpdes) taking into account the maximum input power (Pm), or calculating a maximum pressure (Δpdes_l) that may be generated by the hydraulic pump (4), taking into account the target swivel angle (αdes) of the hydraulic pump (4) calculated in step b and the maximum input power (Pm).