Development repository for Smart Brushless Servo

PID/FOC Custom Firmware for B-G431B-ESC1 board.

Characteristics

1. Hardware (commercial off the shelf)

Product page : https://www.st.com/en/evaluation-tools/b-g431b-esc1.html

Cost: approx. 18$ per unit.

2. Wiring

As mentioned in the user manual, the B-G431B-ESC1 Discovery kit is equipped with a USB connector and different pads for communication, such as:

U4 USB port for programming and debugging
J1 for CAN port
J2 for SWD-STM32F103 (reserved)
J3 for PWM/UART/BECout input/output signal
J4 for SWD-STM32G431 debug/programming port (without daughterboard)
J5/J6 for Lipo battery (30V or 6S max)
J7 for motor
J8 for motor sensor (Hall or encoder)

The USB interface is provided on the daughterboard and it allows to program and debug the main board. It provides also the supply voltage to the STM32G431CB MCU in case of no voltage on the bus (J5 and J6 not connected to the LiPo battery).

For proper operation of the FOC firmware, the J1, J5, J6, J7, an J8 solder pads should be connected. The J2, J3, J4 solder pads may be left unconnected.

For J8, the firmware accept two types of position sensor :

The AS5600 Position Sensor connected through I2C port (https://ams.com/as5600)
The AS5048A High-Resolution Position Sensor connected through PWM interface (https://ams.com/as5048a)

3. Uploading firmware

A full erase of the Chip is strongly recommended, to insure proper initialisation of the default configuration (the last Flash page stores PID/FOC configuration).

The release configuration of the PID/FOC firmware should be built with CubeIDE, and then uploaded using the USB port of the board.

A hard-coded setting must be adjusted by user, according its hardware configuration :

At lines 40+ of main.c,

// Position sensor type :
//    "AS5600_I2C"
//    "AS5048A_PWM"
#define SENSOR_TYPE AS5048A_PWM

4. Local user interface

4.1. Red STATUS LED

The Red STATUS LED is normally OFF.

When an hardware error occurs, the LED is ON.

User may set the LED ON through USB interface.

4.2. Button

A short press on the button starts the calibration sequence. It last a few seconds and the motor turns slowly. Rotor should be free to get a good calibration.

Notice : The number of pole pairs should be configured before starting the calibration sequence. User may set the pole pairs by connecting the ESC to a computer through USB and running the GUI tool.

5. GUI Tool & Controller configuration

GUI Tool allows to configure and to command the controller.

Connect the ESC to USB port, and change the line 20 in SBSUtility.py according serial device:

## change COM port here
servo = servo_protocol2('COM3',1000000)

Run SBSUtility.py

By default, the controller has the ID:1 and USB/VCP baud rate is 1Mbps.

5.1 Configuration registers (EEPROM)

Warning (wear) : Each time a value of an EEPROM register is changed, the Flash is reprogrammed. The number of programming cycles is approx 10.000 to 100.000.

Field	Default Value	Description
ID	1	ID of the controler (used for both USB and CAN). Values: 000h < ID < 010h
Min Position	0	Minimum position in degress, limiting position control
Max Position	1000	Maximum position in degrees (position control)
Max Velocity	5000	Maximum velocity in degrees per second (velocity control)
Max Current	500	Maximum motor current in mA (FOC)
Max Temperature	60	Maximum operating temperaturein °C. Values: <70
Min Voltage	6	Minimum operating power supply voltage. Values: <30
Max Voltage	28	Maximum operating power supply voltage. Values: <30
Encoder Resolution	14	Resolution of the position sensor in bits. Values: 12 for AS5600, 14 for AS5048A
Motor Pole Pairs	14	Pole pairs of the motor
Motor Synchro Angle	0	Offset in degrees between physical and electrical angles. Updated by auto-calibration
Motor Phase Inv	0	Motor phase inversion. Values: {0,1} Updated by auto-calibration
Field Weakening K	255	Field weakening. Values: 255
PID Flux current KP	400	Kp of Flux PI FOC.
PID Torque current KP	400	Kp of Torque PI FOC.

5.2 Control registers (RAM)

Field	Default Value	Description
LED	0	STATUS LED ON/OFF command. Values: {0:OFF,1:ON}
Control Mode	0	Operating mode. Values: {0:IDLE,1:Position/VelocityTorque control}
Goal Position	0	Goal position in degrees (position control)
Goal Velocity	0	Goal velocity in degrees per second (velocity control)
FF Torque Current	0	Feed-forward torque current in mA (FOC, Iq)
Goal Flux Current	0	Reference flux current in mA (FOC, Idref)
Position Kp	0	Kp of Position/Velocity control. Values: 0<Kp<255
Velocity Kd	0	Kd of Position/Velocity control. Values: 0<Kp<255

Warning : A high value of Kp or Kd may damage the actuator.

6. CAN protocol

The controller accepts CAN frame identifier = 000h + its own ID (user configurable ID).

The controler repies with CAN frame identifier = 010h + its own ID (user configurable ID).

6.1. Control frame formats

At start-up (power-on reset), the controller is in IDLE state (motor brake). The position and velocity set-points, the current feed-forward and the Kp and Kd are reset (=0).

In order to arm the controller, a full control frame with a 0xFFFFFFFFFFFFFFFF payload should be sent. The velocity set-point, the current feed-forward and the Kp and Kd are reset (=0). The position set-point is set to the present rotor position.

To disarm the controller, a full control frame with a 0x000000000000000 payload should be send. The position and velocity set-points, the current feed-forward and the Kp and Kd are reset (=0).

The controller disarms it-self automatically, when a CAN bus time-out occur (no control frame received for one second). The position and velocity set-points, the current feed-forward and the Kp and Kd are reset (=0).

For 16-bit fields, low byte first position, high byte second position.

6.1.1. Full control frame

A full control frame has a 64-bit payload.

Field	Length	Value
Position	16b	Position set-point in 1/10 degrees
Velocity	16b	Velocity set-point in degrees per second
Torque	16b	Torque current feed-forward in mA
Kp	8b	Position control
Kd	8b	Velocity control