Drive modes
The term drive mode refers to the low-level control strategy of the motor. Unlike the closed-loop approach, these modes are implemented at a fundamental level, enabling the highest possible dynamic response without increasing the system order. The principles of drive modes are illustrated using a brushed DC motor example (although an AC motor is used in reality) because its characteristics are easier to understand: DC motor current is proportional to torque, and DC motor voltage is proportional to speed. Drive modes have been designed to make AC motors behave in the same way as DC motors would.
- For easy understanding, the modes are depicted with the brushed DC motor.
- This is shared across all ESCx families and all algorithms, although some modes might not be implemented in specific cases.
| Schematic for DC motor | mode | name | Description |
|---|---|---|---|
 | 0 | freewheel (FRW) | Motor freewheels, preferably by disconnecting from the drive. A current can be present due to automatic field weakening, but, the torque is never generated. Motor neither accelerates, nor brakes. |
 | 1 | voltage (VLT) | By setting the specified voltage, a stable speed of the shaft is usually achieved. The torque (and required current) is determined by the load. Torque (current) can be only limited (not controlled) by the user. Motor can accelerate and brake. |
 | 2 | current (CRT) | By setting the specified current, a stable torque of the motor is usually achieved. The speed is determined by the load and could be only limited (not controlled). Motor can accelerate and brake. |
 | 3 | voltage + freewheel (VLF) | By setting the specified voltage, a stable speed of the motor is usually achieved. The torque (and required current) is determined by the load. Torque (current) can be only limited (not controlled) by the user. Motor can accelerate but can not brake, unless the sign of the required voltage is changed. |
 | 4 | voltage brake (VLB) | This mode is the inversion of the mode 3. The motor freewheels from zero RPM until it reaches the specified voltage. After that, currents starts to flow into the battery and motor starts to brake. Motor can not a accelerate in this mode, only brake. |
 | 5 | stator current (SCR) | Similar to mode 2, but the total amplitude of stator current is demanded (not only the Qcomponent as if mode 2). (in BLDC, this mode reduces to mode 2) |
 | 6 | torque (TRQ) | This mode is similar to mode 2, but the driver attempts to control the real torque (with regards to variable flux with d-axis control). (in BLDC, this mode reduces to mode 2) |
 | 8 | brake (BRK) | Brake with constant current. Similar to mode 2, but current has always the direction to generate brake torque. The motor in this mode never accelerates. |
 | 9 | brake torque (BRT) | Similar to mode 8, but real torque is calculated from motor parameters. Real torque (not current) is regulated as in mode 6. (in BLDC, this mode reduces to mode 8) |
 | 10 | brake + freewheel (BRF) | Unidirectional brake with constant torque. For one direction is same as mode 8, for other direction, the motor freewheels. |
 | 15 | brake short (BRS) | Speed-dependent brake. Brake torque is proportional to motor speed. The higher speed, the higher brake torque. The motor in this mode never accelerates. |
*If you request a non-existing mode, the driver will yield into freewheel (mode 0).
- The torque mode (6) and brake torque mode (9) tries to linearize the torque curve and can reduce the maximal current if the
fwcordxcis set (it simply reserves some available current for the d-axis). So if you want to achieve the maximal torque use the current mode (2).
Extended modes
Adding these bits to previous standard modes enables closed-loop extension: engage the PID loop on top.
| Bit | Name |
|---|---|
| 4 | Speed loop |
| 5 | Position loop |
Due to memory constraints, extended modes are not always available. If you do not see folder /driver/pid_speed or /driver/pid_position, the extended modes are not present in your firmware.