Electric Lift Load Sensing via Brake Torque
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Solution Overview
Problem
Existing lift devices rely on hydraulic systems, which require on-board reservoir tanks and frequent maintenance, and lack efficient methods for determining the load supported by the work platform.
Innovation Solution
A fully-electric scissor lift system with a linear actuator having an electric motor and an electromagnetic brake, where the electromagnetic brake is disengaged to determine the motor torque and actuator force, allowing for precise calculation of the load supported by the work platform based on these characteristics and the platform's height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydraulic system is used to support and move the work platform, then the lifting function is achieved, but the system requires on-board reservoir tanks and frequent maintenance
Solution Approach 1:
The patent replaces the hydraulic mechanical system with an electric linear actuator system. The electric motor-driven lead screw mechanism eliminates the need for hydraulic fluid, reservoir tanks, and hydraulic components, thereby reducing maintenance requirements and system complexity while maintaining the lifting function.
Solution Approach 2:
The patent extracts and removes the hydraulic system components (reservoir tanks, hydraulic fluid, hydraulic cylinders) from the lift device, replacing them with a simplified electric actuation system. This extraction eliminates the maintenance burden associated with hydraulic systems.
2Measurement precision
If traditional hydraulic systems are used, then lifting capability is provided, but there is no efficient method for determining the load supported by the work platform
Solution Approach 1:
The patent replaces complex mechanical load sensing mechanisms with an electrical measurement approach. By measuring the electrical current drawn by the electric motor and using mathematical relationships between motor torque, actuator force, and platform height, the system accurately determines load without additional mechanical sensors or complex hardware.
Solution Approach 2:
The patent uses electrical current measurement as an intermediary to infer load information. Instead of directly measuring mechanical load forces, the system measures the electrical parameter (current) that correlates with the mechanical state, providing indirect but accurate load determination through computational relationships.
3Reliability
If the electromagnetic brake is engaged to prevent movement, then safety is improved, but the ability to determine motor torque and actuator force is reduced
Solution Approach 1:
The patent employs periodic engagement and disengagement of the electromagnetic brake. The brake is engaged during normal operation to maintain safety and prevent unintended movement. It is temporarily disengaged during measurement cycles to allow the motor to maintain platform height against the load, enabling accurate torque and force measurements. This periodic switching satisfies both safety and measurement requirements.
Solution Approach 2:
The system uses feedback control where the electromagnetic brake is dynamically controlled based on operational requirements. The control system monitors platform position and load conditions, disengaging the brake when measurement or height maintenance is needed, and re-engaging it when safety is the priority, creating a feedback-based safety measurement coordination mechanism.
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
The system eliminates the need for hydraulic systems and reservoir tanks, reducing maintenance and operational costs, while providing accurate and real-time load determination for safe and efficient operation.
Implementation Method 1
The electromagnetic brake is configured to, when engaged, prevent the linear actuator from moving the retractable lift mechanism between the extended position and the retracted position
Implementation Method 2
maintain a height of the work platform using the electric motor of the linear actuator
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A lift device includes a base, a retractable lift mechanism, a work platform, and a lift controller. The retractable lift mechanism is moveable between an extended position and a retracted position. The work platform is configured to support a load and is coupled to and supported by the retractable lift mechanism. The linear actuator is configured to selectively move the retractable lift mechanism between the extended position and the retracted position. The linear actuator has an electric motor and an electromagnetic brake. The lift controller is in communication with the linear actuator and is configured to determine the load supported by the work platform based on the actuator force applied to the work platform and the height of the work platform.