Electric Drive Roll-Away Control for Slope Holding
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Solution Overview
Problem
Existing methods for preventing rolling away of electric drive motor-equipped mobile machines on inclined surfaces are inadequate as they require the driver to manually position the direction sensor correctly, failing to intervene when the machine rolls in the specified direction of travel, leading to uncontrollable descent.
Innovation Solution
A roll-away protection control unit that applies torque to the drive motor only when the driving command device is deactivated and the rolling direction deviates from the specified direction, using sensors to detect speed and direction, and an inverter to apply voltage, ensuring the machine remains secured against rolling away regardless of driver action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the direction sensor is used to determine whether to apply torque, then the control system can distinguish between intentional and unintentional rolling, but it requires manual positioning by the driver which may fail when the machine rolls in the specified direction
Solution Approach 1:
The system uses the travel command device state (activated/deactivated) to automatically determine whether rolling is intentional or unintentional, eliminating the need for manual direction sensor positioning by the driver. The control unit self-adjusts based on whether the driver has issued a travel command.
Solution Approach 2:
Instead of using the direction sensor to detect rolling direction and compare it with desired direction (which requires manual positioning), the system inverts the logic by using the travel command device state as the primary criterion. When the travel command device is deactivated, any rolling is treated as unintentional regardless of direction.
2Extent of automation
If the travel command device state is used to control torque application, then the system can automatically prevent roll-away without driver intervention, but it may interfere with intentional coasting to stop
Solution Approach 1:
The system applies torque counteraction only partially - specifically when the travel command device is deactivated and rolling speed exceeds a threshold. This allows intentional coasting (when travel command is active) to proceed normally while still providing automatic protection when the driver releases the command device.
Solution Approach 2:
The control unit continuously monitors the state of the travel command device and the rolling speed, and adjusts torque application accordingly. When the driver releases the travel command device, the system detects this state change and automatically applies counter-torque to prevent uncontrolled rolling.
3Reliability
If torque is applied to counteract rolling away, then the machine remains stationary on slopes, but energy is consumed by the drive motor
Solution Approach 1:
The system applies torque periodically or continuously only when needed - specifically when the travel command device is deactivated and rolling is detected. When the driver activates the travel command device or when no rolling occurs, the system stops applying counter-torque, thus conserving energy while maintaining stability when required.
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 solution effectively prevents or reduces rolling away without driver intervention, ensuring the machine remains stationary on slopes by counteracting rolling speed and direction, even when the specified direction of travel is downhill, thus enhancing safety by eliminating the need for manual driver precautions.
Implementation Method 1
an inverter (8) which applies a voltage to the drive motor (2)
Implementation Method 2
a speed sensor (4a) which detects the rolling speed
Implementation Method 3
a direction sensor (4b) which detects the rolling direction of the machine (1)
Implementation Method 4
If such a mobile machine is on an inclined surface, such as a slope, it will roll downwards due to gravity
Data Source
Figure 1
Figure 2
AI summary
A method for reducing a rolling speed, in particular for preventing a mobile machine (1) comprising an electric drive motor (2) from rolling away from a holding position, is described, wherein a speed sensor (4a) detects the rolling speed and a direction sensor (4b) detects the rolling direction of the machine (1) when rolling away, and wherein a holding control unit (3) controls the drive motor (2) depending on the rolling speed and the rolling direction of the machine (1) such that it is subjected to a torque that counteracts rolling away.In order to improve this procedure so that it secures the machine against rolling away independently of any actions required by a driver, it is proposed that the holding control unit (3) should only activate the drive motor (2) to apply torque when a driving control device (5) is deactivated and when the direction of rolling deviates from a signal from a driving direction sensor, in order to reduce the rolling speed and in particular to prevent rolling away.