Brushless DC Motor Control for Worm-Gear Chatter Suppression
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Solution Overview
Problem
Conventional Field-Oriented Control (FOC) methods for brushless DC motors are ineffective in compensating oscillations and vibrations caused by chatter in worm-gear reducers, due to insufficient passband in standard control systems, which limits timely intervention and suppression of the chatter phenomenon.
Innovation Solution
A closed-loop control method for brushless DC motors that renders the stator magnetic field independent of the rotor's orientation, using a PID controller to maintain the angular position of the rotor locked at a 90-degree angle with respect to the stator magnetic field, thereby preventing uncontrolled acceleration and reducing torque through the natural characteristic of torque being proportional to the sine of the angle between the magnetic vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional FOC methods are used to control brushless DC motors in worm-gear reducers, then the control system can maintain reference velocity values, but it cannot effectively suppress chatter vibrations due to insufficient passband
Solution Approach 1:
The patent implements a feedback mechanism where the rotor orientation is measured and used to dynamically adjust the stator magnetic field orientation. The control system continuously monitors the rotor position and feeds this information back to the Clarke-Park transform blocks, enabling real-time compensation of chatter vibrations by adjusting the magnetic field to maintain optimal torque production despite vibrations
Solution Approach 2:
The patent changes the control parameter from fixed stator magnetic field orientation to dynamic orientation that adapts to rotor position. By making the stator magnetic field orientation a variable parameter that changes with rotor orientation (through the feedback loop), the system can adjust to varying operating conditions and suppress chatter effectively
2Power
If the stator magnetic field synchronizes with the rotor in conventional FOC, then efficient torque production is achieved, but uncontrolled acceleration occurs during chatter transitions from static to dynamic friction
Solution Approach 1:
The patent applies preliminary anti-action by intentionally desynchronizing the stator magnetic field from the rotor orientation before chatter occurs. The control system anticipates the instability that would result from perfect synchronization during friction transitions and pre-adjusts the magnetic field orientation to prevent uncontrolled acceleration, counteracting the destabilizing effect before it manifests
3Reliability
If standard closed-loop control is used with sufficient passband to suppress chatter, then vibration control improves, but the system becomes overly complex and difficult to implement
Solution Approach 1:
The patent makes the existing FOC control system multi-functional by enabling it to perform both its primary function of torque production and its secondary function of chatter suppression through the same Clarke-Park transform blocks and feedback mechanism. The existing control infrastructure is enhanced to simultaneously achieve torque control and vibration suppression without requiring separate dedicated control systems
Solution Approach 2:
The control system serves itself by using its own rotor orientation measurement to automatically adjust and compensate for chatter vibrations. The system monitors its own state and self-corrects without external intervention, making the chatter suppression an inherent capability of the control system rather than requiring additional external control mechanisms
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 method effectively suppresses chatter by ensuring the stator magnetic field does not synchronize with the rotor, thereby reducing torque fluctuations and preventing uncontrolled acceleration, even during rapid transitions from static to dynamic friction, without requiring additional hardware or complex interventions.
Implementation Method 1
The idea underlying this technique is to use the so-called Clarke-Park transforms, which enable transformation of the three-phase quantities into two-phase quantities... in a control loop designed to generate electric currents in the three windings of the stator, which are such as to generate the torque required
Implementation Method 2
A closed-loop control method for brushless DC motors that renders the stator magnetic field independent of the rotor's orientation, using a PID controller to maintain the angular position of the rotor locked at a 90-degree angle with respect to the stator magnetic field
Implementation Method 3
obtaining from a corresponding pair of voltages in a reference system of rotation of the motor a triad of phase voltages of the motor, a quadrature voltage of said corresponding pair of voltages being obtained via a closed-loop control procedure that comprises measuring an orientation of the rotor
Data Source
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AI summary
A method for closed-loop control of the velocity of a brushless d.c. motor that supplies a torque (τ) to a rotating mechanical member, including carrying out a control of a FOC (Field-Oriented Control) type (10, 20) comprising obtaining (16), from a triad of stator phase currents (Ia, Ib, Ic) of the motor, a pair of currents (Id, Iq) in a reference system (d, q) of rotation of the motor (15), and obtaining from a corresponding pair of voltages (Vq, Vd) in a reference system of rotation of the motor (15) a triad of phase voltages (Va, Vb, Vc) of the motor (15), a quadrature voltage (Vq) of said corresponding pair of voltages (Vq, Vd) being obtained via a closed-loop control procedure (140) comprising measuring (130) an orientation of the rotor (θ), said control method (100) comprising (110) acquiring a reference angular velocity (ω*) of the motor to be supplied to the control of a FOC type (10, 20); according to the invention, said closed-loop control procedure (140) comprises regulating the orientation of the rotor (θ) to follow a reference orientation (θ*), which forms an angle of 90° with respect to a direction of a stator magnetic field (B), which rotates with an angular velocity equal to said reference angular velocity (ω*).