Hydrostatic Swing Motion Control for Slope Drift Compensation
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Solution Overview
Problem
Conventional systems for determining the position of machines, especially when operating on slopes or with unreliable GPS signals, fail to provide accurate estimates for machine and component positions, and lack the ability to maintain swing components in a stationary state effectively.
Innovation Solution
A closed loop swing motion control system utilizing a hydrostatic pump and hydraulic motor in a closed loop circuit, coupled with a pressure control device and a controller that processes sensor signals from IMUs and non-IMU sensors to adjust pump displacement and pressure, ensuring accurate control of swing mechanisms on slopes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional open loop swing systems are used, then the system is simple to operate, but the swing components drift from commanded positions when the machine is on a slope due to gravity effects
Solution Approach 1:
The patent implements a closed-loop control system that continuously monitors the actual position of swing components using sensors (encoders, inclinometers, GPS) and compares them with commanded positions. The control system calculates position errors and generates corrective commands to actuators, creating a feedback mechanism that actively compensates for drift caused by gravity on slopes, thereby resolving the contradiction between position accuracy and control complexity.
Solution Approach 2:
The patent replaces conventional mechanical position sensing and control methods with electronic sensors and digital signal processing. Instead of relying solely on mechanical feedback mechanisms, the system uses electronic inclinometers, encoders, and microprocessors to detect position and implement corrective actions, reducing mechanical complexity while improving measurement precision.
2Reliability
If low leakage hydraulic control valves are used to hydraulically lock swing components, then drift prevention is improved, but the system complexity increases and reliability decreases
Solution Approach 1:
The patent replaces complex hydraulic locking mechanisms with an electronic control system that uses actuators (hydraulic motors or electric motors) to actively maintain swing component positions. Instead of relying on passive hydraulic locks that require complex valve systems, the invention uses active electronic control with sensors and microprocessors to command actuators that counteract gravitational forces, thereby improving reliability while reducing hydraulic system complexity.
Solution Approach 2:
The control system continuously monitors position errors and automatically generates corrective commands without requiring manual intervention or complex hydraulic locking mechanisms. The system serves itself by detecting drift through sensors and immediately implementing corrections through actuators, eliminating the need for additional complex hydraulic locking components.
3Measurement precision
If GPS data fusion is used for position determination, then position information is enhanced, but the system fails to provide accurate estimates when GPS signals are unreliable or unavailable
Solution Approach 1:
The patent implements a feedback-based sensor fusion system that continuously monitors GPS signal quality and switches to alternative sensing mechanisms when GPS becomes unreliable. The system uses inertial sensors (accelerometers, gyroscopes) and local position sensors (encoders, inclinometers) as backup sources, creating a feedback loop that maintains accurate position estimation even when GPS signals are unavailable, thereby resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The patent prepares for GPS signal failure by implementing redundant positioning systems in advance. The control system includes inertial measurement units and local sensors that are ready to take over immediately when GPS becomes unreliable. This beforehand cushioning ensures continuous accurate position determination without interruption, resolving the contradiction between using GPS data fusion and maintaining reliability during signal failures.
4Manufacturing precision
If a closed loop hydraulic circuit with hydrostatic pump and motor is used, then swing motion control precision is improved, but the system complexity and energy consumption increase
Solution Approach 1:
The patent implements periodic control actions where the closed-loop system continuously monitors position errors and applies corrective forces only when deviations occur, rather than maintaining constant high energy input. The control system uses pulse-width modulation or intermittent actuator activation to maintain precision while minimizing energy consumption, resolving the contradiction between control precision and energy usage.
Solution Approach 2:
The patent employs dynamic control where the hydrostatic pump and motor system adjusts its operation based on real-time position feedback. The system varies pump displacement and motor torque according to actual position errors and gravitational forces, rather than operating at constant high power. This dynamic adjustment maintains swing motion precision while significantly reducing energy consumption compared to static high-power operation.
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
This solution provides precise control and maintenance of swing components' positions, mitigating drift caused by gravity, even on uneven terrain, by using sensor fusion and Kalman filtering to enhance the accuracy of position determination and control.
Implementation Method 1
a hydrostatic swing pump fluidly coupled to at least one hydraulic swing motor configured to control a swing mechanism
Implementation Method 2
a pressure control device configured to control the pressure of fluid supplied to the hydrostatic swing pump for control of the pressure output by the pump
Data Source
AI summary
A swing motion control system for an earth-moving machine may include a closed loop hydraulic circuit including a hydrostatic swing pump fluidly coupled to at least one hydraulic swing motor configured to control a swing mechanism of the earth-moving machine, a pressure control device configured to control the pressure of fluid supplied to the hydrostatic swing pump for control of the pressure output by the pump, and a controller. The controller may be configured to monitor and process signals received from sensors and operator input, wherein the signals received from the sensors are indicative of machine position and pose, and inertia mass of swing components and a payload being moved by the swing mechanism of the machine, and control at least one of an offset amount for desired pump displacement by the hydrostatic swing pump or an offset amount for pump output pressure from the hydrostatic swing pump based on at least one of an amount of slope on which the machine is operating or the inertia mass of the swing components and payload.