Electric Brake Planetary Gear Control for Rapid Force Modulation
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Solution Overview
Problem
Current electric brake systems for vehicles rely on a single motor or hydraulic fluid, which are inefficient in modulating braking force and cannot rapidly adjust to emergency scenarios or drive-away conditions without increasing power consumption.
Innovation Solution
A system utilizing two motors with a planetary gear stage, where the first motor supplies torque to a sun gear and the second motor to a ring gear, allowing for variable speed and direction control of a spindle to modulate braking force on a wheel rotor, enabling rapid application and release of braking force without reversing motor direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single motor is used to control the brake piston, then the device complexity is reduced, but the ability to rapidly modulate braking force and respond to emergency scenarios deteriorates
Solution Approach 1:
The braking system is segmented into two independent motor units (first motor coupled to sun gear, second motor coupled to ring gear) that can operate independently or together. This segmentation allows each motor to contribute differently to brake application - the first motor provides primary braking torque while the second motor enables rapid brake release by rotating the ring gear in reverse, thereby improving braking force modulation speed without excessive complexity
Solution Approach 2:
The system dynamically adjusts the contribution of each motor based on braking requirements. During normal braking, only the first motor operates. During emergency scenarios requiring rapid brake release, the second motor activates to reverse the ring gear rotation, dynamically changing the system's response characteristics to achieve faster modulation speed
2Ease of operation
If motor rotation direction is reversed to release braking in emergency scenarios, then the braking force can be reduced or released, but the response time increases and power consumption rises
Solution Approach 1:
The planetary gear stage acts as an intermediary mechanism between the two motors and the brake piston. The second motor, coupled to the ring gear, serves as a mediator that can rapidly reverse the direction of force transmission to the piston without requiring the first motor to reverse rotation. This intermediary mechanism enables faster brake release by utilizing the mechanical advantage of the planetary gear system
Solution Approach 2:
Instead of reversing the primary first motor to release brakes, the system inverts the approach by using the second motor to rotate the ring gear in the opposite direction. This inversion allows the second motor to counteract the first motor's braking force and rapidly release the brake by exploiting the planetary gear mechanism's ability to reverse force direction efficiently
3Measurement precision
If a planetary gear stage with two motors is used to modulate braking force, then the braking force control precision is improved, but the device complexity increases
Solution Approach 1:
The planetary gear stage serves multiple functions simultaneously: it transmits torque from both motors to the brake piston, provides mechanical advantage for force multiplication, enables bidirectional control of the piston, and allows independent operation of each motor. This multi-functionality achieves precise braking force control without proportionally increasing complexity, as the same gear structure performs multiple critical roles
Solution Approach 2:
The system merges the torque output of two independent motors through the planetary gear stage to control a single brake piston. The sun gear and ring gear are merged into a unified planetary mechanism that combines the rotational inputs from both motors into a single axial force on the piston, achieving precise force control through the combined effect of both motors while maintaining a compact integrated structure
4Adaptability or versatility
If the rotation speed of motors is varied to cyclically move the piston, then the braking force modulation is improved, but the control system complexity increases
Solution Approach 1:
The control system adjusts the rotation speed parameter of the motors to achieve different braking scenarios. By varying the speed at which the first and second motors rotate the sun gear and ring gear respectively, the system can modulate the piston's cyclic movement to provide different levels of braking force. This parameter adjustment enables adaptability to various braking scenarios without requiring fundamental changes to the system architecture
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 allows for precise and efficient control of braking force, reducing power consumption and enabling quicker response to emergency situations and drive-away conditions by varying the speed and direction of the spindle without changing motor rotation direction.
Implementation Method 1
A planetary gear stage includes a sun gear, a ring gear encircling the sun gear. A first motor is coupled to the sun gear. A second motor coupled to the ring gear.
Implementation Method 2
A first motor is coupled to the sun gear. A control system is configured to, in response to a detected braking event, rotate the first motor to supply torque to the sun gear
Implementation Method 3
A second motor coupled to the ring gear. A control system is configured to, in response to a detected braking event, rotate the second motor to supply torque to the ring gear to vary a rotation speed of the spindle without increasing the torque thereon
Implementation Method 4
The service brakes rely on one or more movable pistons that selectively apply force to brake pads in order to slow down or stop rotating wheel rotors on the vehicle
Data Source
AI summary
A system for controlling an electric brake for a wheel rotor having a brake pad associated therewith includes a housing defining a passage. An assembly is provided in the passage and includes a spindle rotatable about an axis and a piston aligned with the brake pad and axially movable in response to rotation of the spindle. A planetary gear stage includes a sun gear, a ring gear, and planetary gears. A first motor is coupled to the sun gear. A second motor coupled to the ring gear. A control system is configured to, in response to a detected braking event, rotate the first motor in a first direction to supply torque to the sun gear while the second motor is rotated in a second direction at varying speeds to supply torque to the ring gear such that the piston is cyclically moved towards and away from the brake pad to modulate a braking force on the rotor.