Question

What knowledge do you need to store in motor control?

Just received the admission notice of graduate students, master's degree in electrical engineering, hope to study in the direction of control, undergraduate mixed for four years, hope that graduate students will not waste three years of time, want to ask what skills the seniors need?

I would like to introduce more about mathematics and share some experience in learning these dry goods!

Answer 1

1. Brushed motor control

In the process, the main thing is to build an MCU, an N tube, and a brushed motor.

In this process, it is necessary to learn to use the MCU output PWM to control the conduction of the N-tube to control the speed of the brushed motor. Of course, an H-bridge can be built in this process to control the forward and reverse rotation and speed of the motor. This process is a very intuitive process and does not require any theoretical knowledge.

You can quickly understand some of the characteristics and control hardware requirements of the motor. Need to know the motor characteristics:

1) The current of the motor under the same voltage, different loads and different speeds, inductively understand the influence of the back EMF of the motor on the current.

2) Understand the phase relationship between the electric phase and the current of the motor, and how the motor itself can achieve commutation. Motor hardware: PWM frequency selection, N-tube model selection, etc. If it involves an H-bridge, it is recommended to learn how to build an H-bridge and the selection of key components.

Motor control: software overcurrent protection, how PWM is generated, and the influence of different PWMs on the motor can be added.

2. Stepper motor control (5 wires)

It is recommended to use a 5-wire stepper motor (with a common line) in this process, because the circuit is simple and easy to drive, using a Darlington tube (UNL2003) to drive. This process should be able to realize motor speed control, overcurrent protection, etc. Motor: The principle and stepping principle of multiphase motor Hardware: MCU is no longer controlled by an IO port, and 4 IOs are needed to control the motor. Software: Realize motor speed regulation to ensure that the motor does not lose steps.

3. Stepper motor control (4 wires)

This process mainly learns H bridge, motor winding, to achieve motor forward and reverse rotation and speed control, motor: mainly learn motor winding hardware: H bridge and key device selection, at this time to start paying attention to the dead zone software: H bridge PWM generation, dead time and so on.

4. Three-phase motor square wave control

This part mainly learns:

Motor: The winding of the motor. To understand the difference between BLDC and PMSM, it is recommended to use PMSM.

Hardware: How to build and understand the 3 half-bridges, it is recommended to learn the drive circuit of the high bridge, understand the principle of pre-charging, etc. Of course, it is possible that using a PN tube does not require pre-charging.

Software:

1) For sensing: commutation can be realized according to the information feedback from Hall. Realize the normal operation of the motor.

2) For non-inductive: 1> learn 3-stage start, 6-step commutation method 2> learn freewheeling shielding 3> understand the principle of motor position detection, and can realize the motor 4 > and sensible comparison, understand the commutation point, motor back EMF and Hall position (motor rotor) relationship

5. FOC control

The first 4, even if you don't have any mathematical knowledge, you can also achieve the operation of the motor through simple emotional understanding.

But when you get to the FOC, you start to enter modern automatic control, and you will use the advanced numbers, linear algebra, differential equations, and automatic control principles you learned in undergraduate. The previous control was basically a black box control, and basically a PID control could solve all control problems.

But when you enter FOC, you begin to enter modern automatic control (some people call it advanced automatic control). The most basic feature of modern automatic control is model-based control. We want to model every object we control. How to build a model? Differential equation. How to solve differential equations: numerical analysis, various observers. Is the control object stable? Whether there can be a solution to a differential equation.

Answer 2

First of all, motor control is divided into three parts, 1) motor body 2) motor control hardware 3) motor control (software), according to what you say, I think you are biased towards the motor control - software part. 

But although these three parts have a priority, they also complement each other. If you have a specific study of one part of the content, you should also learn the other two parts. 

Moreover, motor control is an experimental discipline, the early stage is the most important, the middle and late stage to be realized by theoretical guidance, to pay attention to mathematics, simulation, control theory, each problem should be reproduced through simulation, through mathematical formula derivation to solve real problems. Finally, according to my personal experience, you can refer to the following learning path, if you have any additions, please feel free to propose.

Answer 3

What knowledge do I need to know about motor control?

First, BLDC motor control algorithm

Brushless motors are self-commutation (self-directional conversion), so they are more complex to control.

BLDC motor control requires knowledge of the rotor position and mechanism by which the motor performs rectified steering. For closed-loop speed control, there are two additional requirements, namely measurement of rotor speed and/or motor current and PWM signal to control motor speed power.

Second, the control algorithm

Many different control algorithms are used to provide control of BLDC motors. Typically, a power transistor is used as a linear regulator to control the motor voltage. This method is not practical when driving high-power motors. High-power motors must be PWM controlled and require a microcontroller to provide starting and control functions.

The control algorithm must provide the following three functions:

PWM voltage used to control motor speed

A mechanism for commutation of the motor ingress

A method that uses back EMF or Hall sensors to predict rotor position

Third, the trapezoidal rectifier commutation of BLDC motor

One of the simplest methods for brushless DC motors is to employ so-called trapezoidal rectification commutation.