Controller Modes
The dev_motor_controller main controller offers a user selectable closed loop current controller, or open loop voltage controller. The main controller also offers tests for aligning the rotor to the encoder and deriving the motor phase inductances and resistances.
Controller modes
Set the controller mode by writing an enum to controller_mode:
| Control mode | Description |
|---|---|
current_dq |
Closed loop D/Q axis current controller. |
voltage_dq |
Open loop D/Q axis voltage controller. |
test_align |
Ramp and dwell alignment controller. |
test_dq_l |
D/Q axis inductance test controller. |
test_dq_r |
D/Q axis resistance test controller. |
Controller mode: current_dq
The closed loop controller implements field oriented control to control the motor phase currents in the D/Q axis. The control action is provided by two PI controllers - one for each axis.
Requirements to start:
- Aligned rotor.
- JCS command signals
i_qori_d(either or both) connected.
Note: For general motor operation the signal i_d may be left unconnected.
Configuration parameters
PI current controllers
Configure the current controllers with the following parameters:
| Commands | Type | Required | Description |
|---|---|---|---|
i_d_kp |
float32 | Required | D axis current controller proportional gain (A). |
i_d_ki |
float32 | Required | D axis current controller integral gain (A.s). |
i_d_out_lim_h |
float32 | Optional | D axis current controller output and integrator upper limit (V). |
i_d_out_lim_l |
float32 | Optional | D axis current controller output and integrator lower limit (V). |
i_q_kp |
float32 | Required | Q axis current controller proportional gain (A). |
i_q_ki |
float32 | Required | Q axis current controller integral gain (A.s). |
i_q_out_lim_h |
float32 | Optional | Q axis current controller output and integrator upper limit (V). |
i_q_out_lim_l |
float32 | Optional | Q axis current controller output and integrator lower limit (V). |
Note: If the PI controller output limits are left unconfigured, then the PI controller outputs and integrators will be clamped to the maximum device voltage. It may be useful to set the limits during testing.
Motor torque constant
Setting the motor torque constant converts the incoming command signal from a torque into a current.
If configuring motor_Kt it is advisable to rename JCS command signali_q to something that shows that the command signal is now a torque.
This removes confusion and ensure users are aware that the incoming signal is a torque command, rather than a current command.
| Command | Type | Required | Description |
|---|---|---|---|
motor_Kt |
float32 | Optional | Motor torque constant (Nm/A). Default: 1.0 (effectively disabled) |
Current controller decoupling
Performs decoupling of the D and Q axis.
| Commands | Type | Description |
|---|---|---|
using_vdq_decouple |
boolean | True: Enables D/Q axis decoupling. Default: False |
Ensure the following motor parameters are configured: Good estimates of these parameters are required for satisfactory decoupling performance
| Command | Type | Required | Description |
|---|---|---|---|
motor_Rd |
float32 | Optional | D axis motor winding resistance (Ohm). |
motor_Rq |
float32 | Optional | Q axis motor winding resistance (Ohm). |
motor_Ld |
float32 | Optional | D axis motor winding inductance (Henry). |
motor_Lq |
float32 | Optional | Q axis motor winding inductance (Henry). |
motor_Ym |
float32 | Optional | Flux linkage. |
motor_Kt |
float32 | Optional | Motor torque constant. |
Cogging torque compensation
The current controller features a motor cogging torque compensation mechanism that applies a feedforward current command to the Q axis current controller. The feedforward current is derived from a table of coefficients that map the rotor position to the current required to overcome cogging torque at that position.
The coefficients are generated by an external tool that rotates the rotor under a stiff position control loop, while recording the Q axis current required to hold that position. The motor should be un-loaded and free to spin when generating the coefficients.
As the absolute motor speed increases, torque due to cogging decreases. An envelope may be applied to reduce the cogging torque compensator contribution based on the rotor speed.
An upper envelope region may be defined that reduces the cogging torque feed forward current from full contribution, linearly down to zero contribution.
cogging_compensator_upper_w_m_low defines where the feedforward term begins to reduce its contribution and cogging_compensator_upper_w_m_high defines where the contribution is fully reduced to zero.
| Commands | Type | Required | Description |
|---|---|---|---|
cogging_compensator_coeffs |
float32 | Optional | Array of 1024 compensation coefficients. The compensator will be enabled if any value is non-zero. |
cogging_compensator_upper_w_m_low |
float32 | Required | Start of upper motor speed envelope region, where the cogging torque feedforward contribution starts to be reduced (Rad/s). |
cogging_compensator_upper_w_m_high |
float32 | Required | End of upper motor speed envelope region, where the cogging torque feedforward contribution is fully reduced to zero (Rad/s). |
cogging_compensator_lower_w_m_high |
float32 | Optional | End of lower motor speed envelope region, where the cogging torque feedforward contribution is fully enabled (Rad/s). Set to 0.0f to disable this feature. (default) Experimental: May cause some hunting of the rotor at zero speed. |
Cogging compensation is enabled when any of the cogging_compensator_coeffs are non zero.
If cogging compensation is required then cogging_compensator_upper_w_m_low and cogging_compensator_upper_w_m_high must be configured.
NOTE:
Controller commands and limits may be affected by other health limiting processes. See Health.
Controller mode: voltage_dq
Open loop voltage controller that outputs a voltage command in the D/Q axis.
Requirements to start:
- Aligned rotor.
- JCS command signals
v_qorv_d(either or both) connected.
NOTE:
Controller commands and limits may be affected by other health limiting processes. See Health.
Controller mode: test_align
This mode runs the rotor/encoder alignment procedure by energising the D axis current. Please see Rotor Position Alignment.
Controller mode: test_dq_l
This controller mode attempts to determine either the D or Q axis inductance (H) via frequency injection.
Parameters:
| Command | Type | Required | Description |
|---|---|---|---|
test_ls_dq_test_axis |
enum | Required | Selects either the D or Q axis to apply the test voltage. Options are: measure_test_axis_d measure_test_axis_q |
test_ls_v_dq_bias |
float32 | Required | Bias voltage (V). Should be large enough to lock the rotor, but low enough to avoid over current and over temperatures. |
test_ls_v_dq_amplitude |
float32 | Required | Test square wave amplitude (V), centred around the bias voltage. |
test_ls_test_freq_hz |
float32 | Required | Test square wave frequency (Hz). |
test_ls_test_time_ms |
uint16 | Required | Test duration (ms). |
Once the parameters are written, set controller_mode to test_dq_l to select the D/Q inductance test, then start the test with a write to controller_start.
Poll the status of the test with a boolean read to command controller_is_running.
The boolean value will be true if the controller is running (ie, the test is still running) and false if the controller is in any other state.
Exit the test early with a write to command controller_stop.
Upon test completion read float32 from command motor_Ld or motor_Lq depending on the axis selected by test_ls_dq_test_axis.
The test failed if the return values is 0.0f.
Note: Parameters test_ls_v_dq_bias and test_ls_v_dq_amplitude form the voltage applied to the windings of the motor.
Due to the typically low winding resistances of the motors, large currents may develop for seemingly small voltages.
Either estimate the winding resistance (or measure with a multimeter) to select a reasonable bias voltage or start with small bias voltages (e.g. 1V) and work up.
Controller mode: test_dq_r
This controller mode attempts to determine the D or Q axis resistance (Ohms) via Ohms law.
Parameters:
| Command | Type | Required | Description |
|---|---|---|---|
test_rs_dq_test_axis |
enum | Required | Selects either the D or Q axis to apply the test voltage. Options are: measure_test_axis_d measure_test_axis_q |
test_rs_v_dq_test_amplitude |
float32 | Required | Vd test voltage (V). Should be large enough to lock the rotor, but low enough to avoid over current and over temperatures. |
test_rs_test_time_ms |
uint16 | Required | Test duration (ms). |
Once the parameters are written, set controller_mode to test_dq_r to select the D/Q resistance test, then start the test with a write to controller_start.
Poll the status of the test with a boolean read to command controller_is_running.
The boolean value will be true if the controller is running (ie, the test is still running) and false if the controller is in any other state.
Exit the test early with a write to command controller_stop.
Upon test completion read float32 from command motor_Rd or motor_Rq depending on the axis selected by test_rs_dq_test_axis.
The test failed if the return values is 0.0f.
Note: Parameter test_rs_v_dq_test_amplitude is the voltage applied to the windings of the motor.
Due to the typically low winding resistances of the motors, large currents may develop for seemingly small voltages.
Either estimate the winding resistance (or measure with a multimeter) to select a reasonable bias voltage or start with small bias voltages (e.g. 1V) and work up.
Controller Timing Statistics
The main controller executes within an interrupt routine. The following timing statistics are available to examine the performance of the controller:
| Command | Type | Required | Description |
|---|---|---|---|
ctl_timing_step_max_us |
uint32 | Optional | The maximum ISR execution time (us) |
ctl_timing_step_ave_us |
uint32 | Optional | The average ISR execution time (us) |
ctl_timing_interval_us |
uint32 | Optional | The time interval between ISR calls (us) |
ctl_timing_overrun_count |
uint32 | Optional | Number of ISR overruns |