12-11-2010, 11:06 PM
Yeah, I noticed I made an error on my post, referring to a digitrax manual, should have been soundtraxx of course :-)
Here's a bit from the manual (the diesel user guide) that you might need. Notice they're talking about 'yerkiness' in places, this may be exaggerated if going down hill.
Tsunami’s Hyperdrive system features high-frequency PWM drive for silent motor control along with load compensation (or back-emf) to improve low speed operation and maintain constant speed regardless of changes to the motor load.
The PWM frequency is fixed at 22.000Khz and there are no adjustments.
Tsunami uses back EMF and a PI control loop to sense and control motor speed. There are four CVs associated with the load compensation feature:
CV 10, Back EMF Cutout
CV 209, Kp Coefficient
CV 210, Ki Coefficient
CV 212, BEMF Feedback Intensity
Control Loop Coefficients
Tsunami compensates for load changes by comparing the locomotive’s speed, as measured by the motor’s back-emf voltage, with the current throttle setting. When a difference is detected, the motor voltage is adjusted up or down so that locomotive speed stays constant. This is done using a P-I (proportional-integral) control loop that is tuned using two CVs:
CV 209, Kp, controls the Proportional gain of the control loop and compensates for dynamic changes in the motor load by applying a correction based on the difference between the throttle setting and the current motor speed. This CV may be set between 1 and 255. Higher values produce an increasing level of compensation. However, setting this value too high can lead to irregular and rough performance.
CV 210, Ki, controls the Integral gain of the control loop and compensates for static motor load by applying a correction based on the historical (or integral) difference between the throttle setting and the current motor speed. This CV may be set between 0 and 255. Higher values produce an increasing level of compensation and set the ‘snappiness’ of the control loop. However, setting this CV value too high can lead to oscillations in locomotive speed and we suggest you use the lowest possible setting that still provides optimal performance.
Note: Setting both Kp and Ki to zero will cause the motor to stop.
Strategy for CV Optimization
Finding the right combination of CV settings requires a certain amount of experimentation and patience to get the best performance. Be aware that these settings will also vary from one locomotive to another. Take notes of your CV settings so you can use them as starting points when configuring other locomotives.
Overdoing a particular setting can actually degrade performance so changes should be made in small increments (+/- 10 or so) until the desired performance is attained. The default settings should provide satisfactory performance when used with most HO and N scale motors.
We suggest the following procedure to help fine tune the CV settings:
1. Begin with each CV set to its default value: CV 10 = 0, CV 209 = 25, CV 210 = 20, and CV 212 = 255. In addition, set CV 2 (Vstart) to 0.
2. With the locomotive on level track, set the throttle to around speed step 20.
3. Adjust the value in CV 209 (Kp) with increasingly higher values just until you begin to notice some jerkiness in the locomotive speed. Reduce the setting in CV 209 to the value just before the jerkiness started.
4. Adjust the value in CV 210 (Ki) with increasingly higher values until you begin to notice some oscillation in the locomotive speed whenever the throttle setting is changed. Reduce the setting in CV 210 to the value just before the oscillation started.
Note: When using load compensation, it is unnecessary to set large values into CV 2 (Start Voltage). This is because the load compensation algorithm will automatically adjust the motor power up to reach desired throttle setting. Therefore CV 2 can usually be set to 0 when load compensation is enabled.
Setting the Load Compensation Curve
Tsunami provides two degrees of freedom for controlling the amount of load compensation applied to the motor over the throttle range using CV 10, Back-Emf Cutout and CV 212, Back-Emf Feedback Intensity.
CV 212 sets the amount of load compensation that is initially applied to the motor and may be set anywhere between 0 and 255. A value of 0 disables load compensation altogether while a value of 255 corresponds to full (100%) compensation.
CV 10, Back-Emf Cutout, determines the degree by which the load compensation is reduced as the throttle speed is increased.
When CV 10 is set to 0, the amount of load compensation set by CV 212 is constant over the entire speed range. Setting CV 10 between 1 and 127 will determine the speed step at which the load compensation is reduced to zero as illustrated in the graph on the next page.
Setting CV 10 between 128 and 255 selects a partial reduction of load
Here's a bit from the manual (the diesel user guide) that you might need. Notice they're talking about 'yerkiness' in places, this may be exaggerated if going down hill.
Tsunami’s Hyperdrive system features high-frequency PWM drive for silent motor control along with load compensation (or back-emf) to improve low speed operation and maintain constant speed regardless of changes to the motor load.
The PWM frequency is fixed at 22.000Khz and there are no adjustments.
Tsunami uses back EMF and a PI control loop to sense and control motor speed. There are four CVs associated with the load compensation feature:
CV 10, Back EMF Cutout
CV 209, Kp Coefficient
CV 210, Ki Coefficient
CV 212, BEMF Feedback Intensity
Control Loop Coefficients
Tsunami compensates for load changes by comparing the locomotive’s speed, as measured by the motor’s back-emf voltage, with the current throttle setting. When a difference is detected, the motor voltage is adjusted up or down so that locomotive speed stays constant. This is done using a P-I (proportional-integral) control loop that is tuned using two CVs:
CV 209, Kp, controls the Proportional gain of the control loop and compensates for dynamic changes in the motor load by applying a correction based on the difference between the throttle setting and the current motor speed. This CV may be set between 1 and 255. Higher values produce an increasing level of compensation. However, setting this value too high can lead to irregular and rough performance.
CV 210, Ki, controls the Integral gain of the control loop and compensates for static motor load by applying a correction based on the historical (or integral) difference between the throttle setting and the current motor speed. This CV may be set between 0 and 255. Higher values produce an increasing level of compensation and set the ‘snappiness’ of the control loop. However, setting this CV value too high can lead to oscillations in locomotive speed and we suggest you use the lowest possible setting that still provides optimal performance.
Note: Setting both Kp and Ki to zero will cause the motor to stop.
Strategy for CV Optimization
Finding the right combination of CV settings requires a certain amount of experimentation and patience to get the best performance. Be aware that these settings will also vary from one locomotive to another. Take notes of your CV settings so you can use them as starting points when configuring other locomotives.
Overdoing a particular setting can actually degrade performance so changes should be made in small increments (+/- 10 or so) until the desired performance is attained. The default settings should provide satisfactory performance when used with most HO and N scale motors.
We suggest the following procedure to help fine tune the CV settings:
1. Begin with each CV set to its default value: CV 10 = 0, CV 209 = 25, CV 210 = 20, and CV 212 = 255. In addition, set CV 2 (Vstart) to 0.
2. With the locomotive on level track, set the throttle to around speed step 20.
3. Adjust the value in CV 209 (Kp) with increasingly higher values just until you begin to notice some jerkiness in the locomotive speed. Reduce the setting in CV 209 to the value just before the jerkiness started.
4. Adjust the value in CV 210 (Ki) with increasingly higher values until you begin to notice some oscillation in the locomotive speed whenever the throttle setting is changed. Reduce the setting in CV 210 to the value just before the oscillation started.
Note: When using load compensation, it is unnecessary to set large values into CV 2 (Start Voltage). This is because the load compensation algorithm will automatically adjust the motor power up to reach desired throttle setting. Therefore CV 2 can usually be set to 0 when load compensation is enabled.
Setting the Load Compensation Curve
Tsunami provides two degrees of freedom for controlling the amount of load compensation applied to the motor over the throttle range using CV 10, Back-Emf Cutout and CV 212, Back-Emf Feedback Intensity.
CV 212 sets the amount of load compensation that is initially applied to the motor and may be set anywhere between 0 and 255. A value of 0 disables load compensation altogether while a value of 255 corresponds to full (100%) compensation.
CV 10, Back-Emf Cutout, determines the degree by which the load compensation is reduced as the throttle speed is increased.
When CV 10 is set to 0, the amount of load compensation set by CV 212 is constant over the entire speed range. Setting CV 10 between 1 and 127 will determine the speed step at which the load compensation is reduced to zero as illustrated in the graph on the next page.
Setting CV 10 between 128 and 255 selects a partial reduction of load
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