Accelerometer Feedback for Hydraulic Actuator Flow Limiting
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Solution Overview
Problem
Material handling vehicles face challenges in controlling the movement of attachments to prevent excessive acceleration, which can lead to impacts and inefficiencies, especially when handling varying loads.
Innovation Solution
A control system that includes an accelerometer to sense the acceleration of an attachment, comparing it to a pre-determined limit, and adjusting fluid flow to an actuator via a control valve to limit movement speed, thereby controlling the attachment's movement and preventing excessive acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluid flow to the actuator is increased to improve attachment movement speed, then productivity is improved, but the attachment acceleration becomes excessive causing impacts and safety issues
Solution Approach 1:
The system uses an accelerometer to continuously monitor the actual acceleration of the attachment during movement. This feedback signal is sent to the controller, which compares the measured acceleration against pre-stored acceleration limits for different attachment weights. When excessive acceleration is detected, the controller automatically adjusts the electrohydraulic control valve to reduce fluid flow to the actuator, thereby limiting acceleration to safe levels while maintaining optimal productivity.
Solution Approach 2:
The system dynamically adjusts the fluid flow characteristics to the actuator based on real-time acceleration conditions. The electrohydraulic control valve modifies its opening degree continuously during operation, transitioning between full flow (when acceleration is within limits) and restricted flow (when acceleration exceeds limits). This dynamic control allows the system to adapt to varying load conditions and maintain safe operation across different productivity requirements.
2Object-affected harmful factors
If the control system limits fluid flow to prevent excessive acceleration, then safety and impact prevention are improved, but attachment movement speed decreases
Solution Approach 1:
The system changes the fluid flow parameters dynamically based on acceleration conditions. The electrohydraulic control valve adjusts its flow coefficient (Kv value) in real-time, transitioning between different flow states: unrestricted flow for normal operation, restricted flow when acceleration limits are approached, and fully restricted flow when excessive acceleration is detected. This parameter change allows the system to minimize impact while maintaining maximum productivity during safe operation.
Solution Approach 2:
The control system applies flow limitation only when necessary - specifically when acceleration exceeds pre-determined limits. During normal operation within safe parameters, the valve remains fully open allowing maximum fluid flow and optimal movement speed. The partial action of flow restriction is applied selectively and temporarily only during acceleration events that exceed safety thresholds, minimizing the impact on overall productivity while ensuring safety.
3Object-affected harmful factors
If the system monitors and controls acceleration for all load conditions, then safety across varying loads is improved, but device complexity increases
Solution Approach 1:
The control system is designed with universal functionality to handle all attachment weight conditions through a single integrated controller. The controller stores multiple acceleration limits corresponding to different attachment weights and automatically selects the appropriate limit based on the detected load condition. The same accelerometer, controller, and electrohydraulic valve assembly serve all safety monitoring and control functions across the entire operating range, eliminating the need for separate control systems for different load conditions.
Solution Approach 2:
The system performs self-adjustment based on the detected attachment weight and corresponding acceleration characteristics. The controller automatically retrieves the appropriate acceleration limit from its stored data, compares it with the actual acceleration measured by the accelerometer, and adjusts the valve position accordingly without external intervention. This self-service capability allows the system to adapt to varying loads autonomously, maintaining safety across all conditions without requiring complex external control mechanisms.
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 effectively manages attachment movement, reducing impacts and improving efficiency by adjusting fluid flow based on sensed acceleration, ensuring safe and efficient operation across different load conditions.
Implementation Method 1
an accelerometer is connected to the vehicle, is configured to sense an acceleration of the attachment, and to communicate the sensed acceleration to the control system
Implementation Method 2
A fluid reservoir is fluidly connected to the actuator to control movement of the attachment, and a control valve is positioned between the fluid reservoir and the actuator to selectively limit flow to the attachment
Data Source
AI summary
A control system for a material handling vehicle has a boom arm connected to a vehicle frame for rotation about the vehicle frame. An actuator is connected to the vehicle frame and the boom arm to cause the boom arm to rotate about the vehicle frame, and an attachment is connected to the boom arm for rotation with respect to the boom arm. The control system includes a controller that is configured to calculate a pre-determined acceleration limit of the attachment, and a sensor that senses acceleration of the attachment and communicate the sensed acceleration to the controller. The controller is configured to compare the pre-determined acceleration limit of the attachment to the sensed acceleration of the attachment and is configured to adjust a control valve to limit flow to the actuator in response to the sensed acceleration of the attachment being above the pre-determined acceleration upper limit.