Brake System Control via Speed-Limited Field Weakening Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing brake systems with electronically commutated synchronous machines face inefficiencies and instability at high speeds due to excessive magnetic field weakening current, leading to increased ohmic losses and delayed actuation times.
Innovation Solution
A method for controlling the brake system that limits the magnetic field weakening current based on rotational speed, using a characteristic map to determine the target current value, ensuring it does not exceed a maximum, and adjusting it according to the instantaneous supply voltage, thereby maintaining efficient operation and rapid pressure build-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If magnetic field weakening current is increased to achieve higher rotational speeds, then the speed capability of the synchronous machine is improved, but ohmic losses increase and efficiency deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the magnetic field weakening current based on the actual rotational speed. Instead of applying excessive field weakening current to ensure high-speed capability, the system adapts the current magnitude to match the actual operating speed, thereby reducing ohmic losses while maintaining the ability to operate at high speeds when needed.
2Adaptability or versatility
If magnetic field weakening current is increased to extend speed range, then the operational speed range is improved, but control stability deteriorates at high speeds
Solution Approach 1:
The patent implements feedback control by continuously monitoring the actual rotational speed and using this information to adjust the magnetic field weakening current. The control unit receives speed feedback and adapts the field weakening current accordingly, preventing excessive current application that would cause instability while maintaining extended speed range capability through adaptive current adjustment.
3Reliability
If field weakening controller maintains voltage reserve by applying larger field weakening current, then voltage reserve is improved for new setpoints, but settling time increases
Solution Approach 1:
The patent applies partial action by adjusting the magnetic field weakening current to match the actual operational requirements rather than maintaining excessive current for all conditions. The system applies just enough field weakening current to achieve the desired speed and maintain voltage reserve, avoiding the excessive current application that would increase settling time while still ensuring adequate voltage reserve for new setpoints.
4Speed
If excessive magnetic field weakening current is applied, then high-speed operation is enabled, but actuation time increases
Solution Approach 1:
The patent applies dynamics by making the magnetic field weakening current adaptive rather than static. The control system dynamically adjusts the field weakening current based on real-time speed feedback, enabling high-speed operation when needed while reducing the current when lower speeds are sufficient, thereby minimizing actuation time while maintaining high-speed 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
This approach stabilizes motor control at high speeds, reduces ohmic losses, and enables rapid and reliable pressure build-up, ensuring consistent performance even with fluctuations in supply voltage.
Implementation Method 1
an electric machine (44), in particular an electronically commutated synchronous machine
Implementation Method 2
a cylinder-piston arrangement (110) with a hydraulic pressure chamber (112) and a piston (111)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method for operating a brake system for motor vehicles, by means of an electrically controllable pressurising system which comprises a cylinder-piston unit with a hydraulic pressure chamber and a piston movable by an electromechanical actuator, a plurality of hydraulic wheel brakes associated with at least one axle of the vehicle and which can be supplied with braking pressure via the hydraulic pressure chamber, and a sensor for detecting the driver's intention to brake, the electromechanical actuator comprising a rotation-translation transmission and an electronically commutated synchronous machine having a stator with at least two phase windings, a rotor comprising at least one permanent magnet and at least one rotor position sensor. In this method, a torque-forming current (iq) and/or a magnetic field attenuating current (id) are adjusted in a co-ordinate system which is fixed relative to the rotor, voltages in the co-ordinate system fixed relative to the rotor are detected to serve as control variables, and are transformed, on the basis of the measured rotor position, into a voltage phasor which indicates for each phase winding of the stator a voltage to be applied, and a set value for the magnetic field attenuating current (id) is limited to a maximum value depending on the measured speed of rotation of the rotor, said maximum value being preferably determined from a predetermined characteristic map. The invention further relates to an electronic controller and to a brake system.