Hi
I want to drive jrk 21v3 with the analog input.
The power supply is 15v. I connected the Rx pin and ground pin to my analog input source.(0~5v)
I also used the “learn” button in the input tab of Pololu UI to calibrate.
However, the output to the motor is not linear( input 0~5v should have output -15~15v)
The output has a large deadzone at the input from 3.3~1.7 and the linear range is also narrow.
Is my setup wrong?
Thank you
Austin
Hello, Austin.
How are you determining that the output is not linear? Are you measuring the voltage across the motor terminals on the jrk, or are you looking at the motor’s speed? Is the motor connected, and if so, is there a load on the motor? Could you also post your jrk setting file, so I can take a look for anything that might be causing the behavior you are observing?
- Grant
Hi
I measured the voltage cross the motor and there is no load to the motor.
Even I remove the motor and measure the voltage(motor outputs, A and B)
It is still not linear. analog input signal through Rx is form 0~5V
The following is my motor setting.
INITIALIZED 0
INPUT_MODE ANALOG
INPUT_MINIMUM 88
INPUT_MAXIMUM 4092
OUTPUT_MINIMUM 0
OUTPUT_NEUTRAL 2048
OUTPUT_MAXIMUM 4095
INPUT_INVERT 0
INPUT_SCALING_DEGREE 1
INPUT_POWER_WITH_AUX 0
INPUT_ANALOG_SAMPLES_EXPONENT 5
INPUT_DISCONNECT_MINIMUM 44
INPUT_DISCONNECT_MAXIMUM 4093
INPUT_NEUTRAL_MAXIMUM 2182
INPUT_NEUTRAL_MINIMUM 2182
SERIAL_MODE USB_DUAL_PORT
SERIAL_FIXED_BAUD_RATE 9600
SERIAL_TIMEOUT 0
SERIAL_ENABLE_CRC 0
SERIAL_NEVER_SUSPEND 0
SERIAL_DEVICE_NUMBER 11
FEEDBACK_MODE NONE
FEEDBACK_MINIMUM 0
FEEDBACK_MAXIMUM 4095
FEEDBACK_INVERT 0
FEEDBACK_POWER_WITH_AUX 0
FEEDBACK_DEAD_ZONE 0
FEEDBACK_ANALOG_SAMPLES_EXPONENT 5
FEEDBACK_DISCONNECT_MINIMUM 0
FEEDBACK_DISCONNECT_MAXIMUM 4095
PROPORTIONAL_MULTIPLIER 0
PROPORTIONAL_EXPONENT 0
INTEGRAL_MULTIPLIER 0
INTEGRAL_EXPONENT 0
DERIVATIVE_MULTIPLIER 0
DERIVATIVE_EXPONENT 0
PID_PERIOD 10
PID_INTEGRAL_LIMIT 1000
PID_RESET_INTEGRAL 0
MOTOR_PWM_FREQUENCY 1
MOTOR_INVERT 1
MOTOR_MAX_DUTY_CYCLE_WHILE_FEEDBACK_OUT_OF_RANGE 200
MOTOR_MAX_ACCELERATION_FORWARD 600
MOTOR_MAX_ACCELERATION_REVERSE 600
MOTOR_MAX_DUTY_CYCLE_FORWARD 600
MOTOR_MAX_DUTY_CYCLE_REVERSE 600
MOTOR_MAX_CURRENT_FORWARD 0
MOTOR_MAX_CURRENT_REVERSE 0
MOTOR_CURRENT_CALIBRATION_FORWARD 37
MOTOR_CURRENT_CALIBRATION_REVERSE 37
MOTOR_BRAKE_DURATION_FORWARD 0
MOTOR_BRAKE_DURATION_REVERSE 0
MOTOR_COAST_WHEN_OFF 0
ERROR_ENABLE 70
ERROR_LATCH 70
Thanks
Austin
From looking at your settings, I noticed your feedback mode is set to “None”. When the feedback mode is set to “None”, a target of 2648 corresponds to full speed forward (likewise a target of 1448 corresponds to full speed reverse). More information about this can be found in the “Feedback Options” section of the jrk user’s guide. This also means that with these settings, any target set above 2648 will result in a duty cycle of 100% (and any target below 1448 will result in a reverse duty cycle of 100%). Changing the target maximum and minimum values in the “Scaling” section of the input tab to 2648 and 1448 respectively, should allow you to use the full analog input range of 0 to 5V.
With the motor disconnected, do you still see non-linear behavior or a dead zone near the neutral point? If so, could you send some screen captures of the plots from the jrk configuration utility that demonstrate the behavior (The plots can be accessed by clicking on the small graph in the top right hand corner of the Jrk Configuration Utility.)?
- Grant
Hi Grant,
Thanks for the help. The new setting works.
And there is no nonlinear region near the dead-zone, when I disconnected the motor.
Austin