Electric Working Machine Powertrain Control for Wheel Spin Prevention
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Solution Overview
Problem
Electrically powered work machines experience undesirable wheel spinning during deceleration due to high inertia in the drive train, leading to unwanted digging into the ground when the braking force is lower than the driving force caused by the motor's inertia.
Innovation Solution
Implement a situation detection system using various sensors to predictively recognize impending speed decelerations and apply current in the opposite direction to the traction motor to generate an additional braking torque, counteracting the motor's inertia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric motor operates at high speed with high mass inertia to provide sufficient power, then the power output is improved, but the wheel spinning and unwanted digging into the ground occurs during deceleration
Solution Approach 1:
The control system applies a counteracting torque to the electric motor before and during deceleration events. When deceleration is detected (such as when the bucket plunges into earth), the controller generates a braking torque by applying current in the opposite direction to the motor's operating direction, counteracting the motor's inertia and preventing wheel spinning before it occurs.
Solution Approach 2:
The high inertia of the electric motor, which causes harmful wheel spinning during deceleration, is converted into a beneficial feature for acceleration. The control system recovers kinetic energy during deceleration by operating the motor as a generator, feeding energy back to the battery, and then utilizing this stored energy for subsequent acceleration phases, transforming the harmful inertia into useful acceleration power.
2Force
If mechanical friction brakes are used to achieve deceleration, then the braking force is improved, but the wheel spinning and digging into the ground worsens due to insufficient braking force relative to motor inertia
Solution Approach 1:
The braking system merges two braking mechanisms: mechanical friction brakes and electromagnetic braking through the electric motor. The control system coordinates both systems, using the motor's electromagnetic torque (generated by applying current in the opposite direction) in conjunction with mechanical brakes, to provide sufficient total braking force to overcome the motor's high inertia and prevent wheel spinning and digging into the ground.
3Object-affected harmful factors
If the electric motor speed is reduced during deceleration, then the wheel spinning is prevented, but the power output capability is reduced
Solution Approach 1:
The control system employs periodic action by alternating between acceleration phases (using the motor in motor mode) and deceleration/energy recovery phases (using the motor in generator mode). During deceleration, the motor operates as a generator to recover energy and control speed, then during subsequent acceleration phases, the recovered energy and battery power are utilized to maintain power output capability, creating a periodic cycle that prevents wheel spinning while preserving overall power capability.
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
Prevents wheel spinning by effectively reducing the traction motor's speed and maintaining vehicle control during external decelerations, ensuring stable operation without digging into the ground.
Implementation Method 1
the travel motor (31) is supplied with current in the opposite direction to its operating direction
Implementation Method 2
apply current in the opposite direction to the traction motor to generate an additional braking torque, counteracting the motor's inertia
Implementation Method 3
Implement a situation detection system using various sensors to predictively recognize impending speed decelerations
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method for operating an electric powertrain (11) for a working machine (10). The powertrain (11) comprises a working drive (20) with an electric drive motor (21) and a travel drive (30) with an electric travel motor (31) and vehicle wheels (32), wherein the working machine (10) is subjected to a negative acceleration from the outside, and a braking force acting on the vehicle wheels (32) as a result of the negative acceleration can be lower than the drive force acting on the vehicle wheels (32) as a result of the moment of inertia of the travel motor (31). The method according to the invention is characterized in that the travel motor (31) is energized (300, 301) opposite the operating direction of the travel motor in order to reduce the rotational speed if a situation detection process predicts that the braking force acting on the vehicle wheels (32) as a result of the negative acceleration is lower than the drive force (200) acting on the vehicle wheels (32). The invention additionally relates to a corresponding electric powertrain (11) and a corresponding working machine (10).