| Moto 1.0 PWM-Encoder Mode |
Last Modified: 2006-08-16
About PWM-Encoder Mode
In PWM-Encoder Mode, the Moto Module drives a motor or other high-current device with variable speed (using PWM ) in positive and negative directions. In addition, the Moto application displays the encoder inputs, which can be used for diagnosing and understanding how the encoder input relates to the output speed. This type of speed control is open-loop; that is, no feedback from the driven device is fed back into the control system. This mode is useful for testing out a new motor or H-Bridge and verifying the encoder direction and operation.
The Moto 1.0 Application in PWM-Encoder Mode
You can manipulate seven variables in PWM-Encoder Mode:
This mode affects the duty cycle of the PWM signal, which effectively varies the voltage to the motor and varies the speed. The duty cycle is set using the throttle slider. The center point of the slider is neutral. Sliding the set point above the center point moves the motor in one direction; sliding it below the center point moves the motor the other direction. The stop button returns the throttle to the neutral position and stops the motor.
The input offset is added to the encoder input to enable a centering offset adjustment. With encoders, this is not typically needed and the value is usually set to zero. In other modes, this can be used to adjust the neutral input setting to zero.
This setting can vary between 0 and 32767 and puts a limit on the maximum PWM output allowed. You can use this value to:
The default for this value is no limit or 32767 (the PWM maximum).
The period is how many timer increments (0.1 ms) pass between encoder measurements. This input is a velocity measurement as its units are encoder ticks / time. Depending on your encoder resolution, you may want to adjust the period to give a reasonable maximum value. Values that range from 100 to 300 when the motor is running at full speed give plenty of dynamic range for the motion control equations.
This value represents the PWM frequency in Hz. The default is 39,062 Hz, which is a reasonable starting point. To get maximum efficiency from your system, we recommend a frequency above 20 kHz. This value is out of the audible range (for humans) so it also provides quiet motor operation. When entering a new PWM frequency, you may not get the exact value you entered. The controller generates a fixed number of different PWM frequencies and the program must select a frequency that is the closest match.
Checking this box inverts the encoder input. This enables you to match the signs of the PWM output and encoder input. A positive output should produce a positive input and a negative output should produce a negative input. If the output and input have opposite signs, the motion control algorithms agressively seek the farthest position from the set point, rather than trying to settle into it.
Checking this box inverts the PWM output signal. This reverses the motor direction. You may want to reverse a motor when using two motors on a differential-drive robot so that positive PWM values mean forward motion for both motors.
The basic logic flow of the PWM-Encoder Mode of operation.
| voice: 720-564-0373, email: email@example.com, address: 4822 Sterling Dr., Boulder CO, 80301-2350, privacy |
© Copyright 1994-2012 Acroname, Inc., Boulder, Colorado. All rights reserved.