The driving method of DC brushed motor is essentially to use H-bridge circuit for driving.
The brushless motor is also
driven by an
H- bridge circuit, but
each phase of the motor is driven by a half-bridge circuit .
Three-phase brushless motors require a total of three half-bridges, unlike DC brushed motor drives that use a full-bridge circuit.
The stepper motor cannot be directly connected to the DC or AC power supply, and must be connected to a dedicated driver to work normally
Servo motor driver (
servo drives) is a controller used to drive and control the servo motor.
The servo motor driver receives and amplifies the command signal from the control system, and transmits the current to the servo motor to generate a signal proportional to the command signal. exercise.
These command signals usually control parameters such as the position, speed and torque of the servo motor to achieve high-precision positioning of the transmission system.
. Sensors attached to the servo motor feed back the actual state of the motor to the servo drive, which compares the actual motor state with the commanded state from the control system. The driver then varies the voltage, frequency or pulse width to the motor to correct any deviation from command.
Voltage control , changing the characteristics of the motor by changing the magnitude of the voltage;
Current control,
controlling the magnetism of the two magnets can also control the rotation of the motor.
current calibration
It must be noted that in the hardware design, instead of using
0v as the initial voltage, a bias of
1.24v
is added
, see the figure for details
Go to V 1.24
in
the single-ended output result . Therefore, in our program, using flflag, when the motor does not start after the development board is powered on, first collect 17 bias voltage data ( the bias voltage after 17 data collections in the actual measurement is more accurate, this number and the time it takes for the circuit to reach a stable state Related ) , and then save the bias voltage, here use static to define adc_offffset. Finally, every time the current value is obtained, the offset voltage will be subtracted to ensure that the data is correct.
ADC_AnalogWDGConfTypeDef
ADC
Analog Watchdog
After configuring
the upper and lower overflow limits of the ADC analog watchdog and enabling interrupts, we can use the
ADC analog watchdog peripheral to detect abnormalities in the circuit voltage. When the circuit is abnormal, the watchdog will trigger an interrupt callback,
Analog steering gear
The internal control drive circuit board receives control signals from the outside, and after processing, it becomes a DC bias voltage, which is inside the control board
There is a reference voltage which is generated by the potentiometer and fed back to the control board. Combine the externally obtained DC bias voltage with the power
Compare the voltage of the bit device to obtain the voltage difference, and output it to the motor driver chip to drive the motor. The positive or negative of the voltage difference determines the positive or negative of the motor.
Reverse, the size determines the angle of rotation, when the voltage difference is
0
, the motor stops rotating. The general block diagram is shown in the figure below.
The three closed-loop control of the industrial servo motor is simplified to only one position closed-loop. The name of the steering gear is a common name in China, which is essentially a servo motor.
The control of the steering gear usually adopts
PWM
signal, for example, a
pulse width modulation ( PWM ) with a period of
20ms is required, and the pulse width
The degree part is generally
the angle control pulse part in the range of
0.5ms-2.5ms , and the total interval is
2ms . When the pulse width is 1.5ms, the steering gear rotates to the middle angle, the steering gear rotation angle increases when it is greater than 1.5ms , and the steering gear rotation angle decreases when it is less than 1.5ms .
0.5ms corresponds to 0 degrees, 2.5ms corresponds to the maximum rotation angle, and the pulse width and rotation angle are also linearly related.
stepper motor
The power-on sequence in the figure is: A->AB->B->BC->C->CD->D->DA The
rotor only walks half a step of
45 degrees each time, so this is also called half-step drive, which is the same as Full step rotation is smoother than half step rotation.
Number of phases : the number of pairs of exciting coils that generate different polar N and S magnetic fields
Number of beats : the number of pulses or conduction state required to complete a periodic change of the magnetic field is
represented by n.
There is a four-phase four-beat operation mode, that is, AB-BC-CD-DA-AB, and a four-phase, eight-beat operation mode, that is, A-AB-B-BC-C-CD-D-DA-A.
Step angle : the angle of motor rotation corresponding to a pulse signal
Positioning torque : When the motor is not powered, the locking torque of the motor rotor itself
(caused by the harmonics of the magnetic field tooth profile and mechanical errors).
Static torque : the locking torque of the motor shaft when the motor is under the rated static voltage and the motor does not rotate. This torque is a standard to measure the volume of the motor, and has nothing to do with the driving voltage and driving power.
Step angle accuracy : The error between the theoretical value and the actual value of the stepper motor rotating a step angle.
Out of step : The number of steps that the motor runs when it is running is not equal to the theoretical number of steps. It can also be called step loss, which is usually caused by too much load or too fast frequency.
• Misalignment angle : The angle at which the rotor tooth axis deviates from the stator tooth axis. There must be an misalignment angle in the operation of the motor. The error caused by the misalignment angle cannot be solved by subdivision driving.
•
Maximum no-load starting frequency : the maximum frequency that can be started directly without loading.
•
Maximum no-load running frequency : the highest speed frequency of the motor without load.
• Running torque characteristics : The dynamic torque of the motor depends on the average current (rather than static current) when the motor is running. The greater the average current, the greater the output torque of the motor, that is, the harder the frequency characteristic of the motor.
•
Motor forward and reverse control : Change the forward and reverse of the motor by changing the power-on sequence.
Brushless motors basically must pass through a brushless controller to achieve continuous operation.
Actual speed
= KV
value
* working voltage. The physical meaning of KV
is
the speed per minute at a working voltage of 1V. The speed of the motor will increase linearly as the voltage increases
Two-two conduction mode of three-phase star connection.
Different voltages need to be connected to the rotor to rotate, and each voltage change is called commutation.
Three-phase six-arm full-bridge drive circuit.
We don't know which two MOS transistors should be turned on in the first step , so here we need to know the position information of the rotor . However, continuous position information is not required, only the position of the commutation point needs to be known. There are generally two ways to obtain the rotor position, one is to use a sensor, and the other is not to use a sensor. Here we take the Hall sensor as an example.
In the control of
the MOS
tube, there are two special situations that need to be paid attention to:
1. When the
MOS tube is turned on
according to the corresponding Hall value in the truth table
, and the conduction state remains unchanged , the motor will rotate to the corresponding position.
The corresponding position remains unchanged , at this time the electrical energy in the circuit can only be converted into thermal energy , not mechanical energy, and our electrical
The machine winding is enamelled copper wire, its internal resistance is very small, and the current will be very large, which will generate a lot of heat and cause
Cause the power supply or motor to be burned . (to keep turning)
2.
In the above schematic diagram of the three-phase six-arm full-bridge drive circuit, if
Q
1
and
Q
2 are turned on at the same time, or
Q 3 and Q 4
are turned on
, or
Or turn on
Q
5
and
Q
6
, as long as the above two corresponding
MOS
tubes are turned on, the motor in the circuit will not work normally
operation, and
the MOS
tube directly connects the positive and negative poles of the power supply , which will undoubtedly burn the power supply or the
MOS
tube. (short circuit)