Motor Amplifier Specifications Menu
The Motor Amplifier Specifications menu options described below allow you to set values for the amplifier including the motor sign and the DAC limits which protect the motor and system hardware by limiting the output commands.
For an overview of how these parameters impact Amplifier control in the Adept SmartMotion system, see Amplifier Control.
When you select a menu option, the following information is provided on screen:
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Instructions for the specified option
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Current value
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Value range for the parameter if applicable
For details on a menu option, click the desired link in the following list to view the description:
Maxiumum DAC output in Manual mode
*Duty-cycle exceeded* DAC limit
*Duty-cycle exceeded* filter parameter
Manual mode envelope error limit
Axis error time delay configuration
Skew error limit (only available if split-axis configuration is selected)
Menu Option Descriptions
Change Motor Number
Use this option to select a different motor for tuning. The currently selected motor is indicated in the menu page title.
Motor Sign
The servo control loop will generate a torque command proportional to the position error. If that torque command has the wrong sign, it sends the motor in the wrong direction, increasing the position error, which increases the torque, which increases the position error, and pretty soon you have a runaway motor. The motor sign allows you to make sure the torque command acts in the proper direction to correct errors, not make them worse! You simply have to make sure that a positive torque command causes motion in the positive direction; if not, reverse the motor sign. A non-zero value for the motor sign tells the control system to invert the torque commands before sending them to the DAC.
The motor sign can be tested with the Perform hardware diagnostics selection. Follow the instructions in Test and Troubleshooting to perform the test.
WARNING: If after finding the correct value for the motor sign, you need to redefine which direction of motion is considered positive, be sure to change both the encoder sign and the motor sign together. Changing only the encoder sign or motor sign can lead to a runaway motor. Exercise great caution when setting this parameter.
Maximum DAC Output
It is possible to limit the output of the analog DAC command using this parameter. This is useful as a safety feature to limit the maximum torque or velocity (depending on the type of drive). Setting this parameter defines both the positive and negative limit of the DAC. The maximum DAC output is 10 VDC, which corresponds to a command of 32767. If this parameter is set to zero, various errors (such as *Motor stalled*) will be generated if any motion or calibration commands are executed. By initially setting this parameter smaller than its eventual value, the DAC output limit can be used to limit any potential damage to hardware during the specification procedures. An initial value of 10% of full-scale is recommended, until you have completed servo tuning as described later in this chapter.
Maximum DAC Output in Manual Mode
This value specifies the maximum output the servo can send to the DAC during Manual Control mode. It should not exceed the maximum DAC output value.
*Duty-cycle Exceeded* DAC Limit
The duty-cycle limit is one of the safety features V+ provides to prevent overexerting your motor or drive system. During operation, the root mean square (RMS) DAC output value is fed into an averaging filter. If the filtered RMS value ever exceeds the value of this parameter, a *Duty-cycle exceeded* error is generated and high power is disabled. Typically, this value is about 2/3 of the maximum DAC output, and it can be disabled by setting it to be zero, or greater than the maximum DAC output.
*Duty-cycle Exceeded* Filter Parameter
This value specifies the low-pass filter through which the root mean square (RMS) DAC value is fed before comparing it to the above limit. By filtering the DAC output, momentarily high torque commands will not cause an error. The more filtering, the longer it will take for an error to be declared. In order to help you set this value, use the following rule of thumb: assuming the DAC output is at a constant value, the "rise time" of the DAC filter to 63% of the DAC output value is 2n milliseconds, where n is the filter parameter. A value less than 5 will give a "hair-trigger" response, causing the *Duty-cycle exceeded* error very soon after the "*Duty-cycle exceeded* DAC limit" is exceeded. A value of 9 (approximately 1/2 second rise time) is recommended.
*Motor Stalled* Timeout
To further protect the system from damage, motor-stall detection is incorporated at the servo control level. When full torque is commanded for the specified amount of time, the robot is assumed to be stalled, high power is disabled, and a *Motor stalled* error is generated.
*Soft Envelope Error* Limit
The envelope error, also known as the following error, is defined as the lag between the commanded and actual position during a motion. This error value gives an indication of how well the mechanism is following the commanded motions. The Adept SmartMotion software monitors the envelope error during execution of motions and compares these values against this parameter. If the specified limit is exceeded, a *Soft Envelope error* message is generated. The motion comes to a controlled stop. However, the High Power stays on. This parameter can also assist in detecting encoder failure during operation.
*Hard Envelope Error* Limit
The Hard Envelope error differs from the Soft Envelope error in that if the specified limit is exceeded, High Power is turned off immediately. It should be set to a value greater than the Soft Envelope error value.
Manual Mode Envelope Error Limit
Specifies the servo position error limit for manual mode. The value is specified in encoder counts. When this limit is exceeded, a *soft envelope error* message is displayed, the motion comes to a controlled stop, but the arm power remains ON.
Velocity envelope error menu
Specifies the servo velocity error limit in Current mode which is only active during calibration. In this mode, there is a potential danger that the robot will run away. When the limit is exceeded, a *hard envelope error* message is displayed and High Power is disabled immediately.
Machine Input Polarity
You can control whether various signals are active-high or active-low using the machine input polarity value. This allows you more flexibility in your choice of sensors.
Four bits are used to determine the polarity of the Home Switch, the Positive and Negative Overtravel Switch and the Drive Fault Signals:
Bit 0 is set when the Home switch is active high*
Bit 1 is set when the Positive Overtravel is active high
Bit 2 is set when the Negative Overtravel is active high
Bit 3 is set when Drive Fault is active high
*Active high indicates that current flows into the input when active.
The Machine Input Polarity menu option provides a table for the Machine Configuration Word. Enter the value that corresponds to the desired sensor settings.
Axis error time delay configuration
The axis error time delay configuration specifies a time period in which axis errors are not monitored after the amplifier power is enabled. This acts as a filter for noise errors caused by powering up the amplifier. The following selections are available:
Value
Description
0
No time delay
1
0.125 sec
2
0.250 sec
3
0.500 sec
4
0.750 sec
5
1.000 sec 6
1.500 sec
7 3.000 sec
Skew error limit (only available if split-axis configuration is selected)
This parameter defines the maximum skew error (difference between the position errors of the split axes of a gantry allowed before a *Skew Error* is sent to V+. It is in units of encoder counts.
Default motion speed
This value specifies the default speed of a motor during servo-controlled trajectories. Most trajectories are V+ controlled. Currently, only motions that axes of a split-axis mechanism are servo controlled. A value of 4 counts/millisecond is typical.
Perform hardware diagnostics
Displays the Perform hardware diagnostics menu to test the new parameters specified using the Amplifier Specifications menu. See Perform hardware diagnostics for details.