Download Inertia Identification

Inertia Identification
Introduction
• What is Inertia?
– Inertia is the resistance of an object to rotational
acceleration
– Anything that is rigidly coupled with the motor
shaft
– Example: The drum of a washing machine
• What is NOT Inertia?
– Anything that does not immediately change
directions with the motor
– Example: Clothes/Water in a washing machine
Example of What is Inertia
Simple Motion System
Load
Identifying Inertia
Rotation
Rotation
Motor
Motor
Rotating Mass
Rotating Mass
Disconnected
Non-Rotating
Mass
Non-Rotating
Mass
Importance of Inertia
• Why is Inertia Important?
– Represents the amount of mass the motor is
rotating
– Informs speed controller how strongly to respond
to disturbances
– Allows for the most responsive speed control
– Direct Input to SpinTAC Speed Controller
SpinTAC Velocity Identify
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Identifies the system inertia
Simple, one-button operation
Accurate and repeatable inertia result
Compensates for the influence of friction
Only run during development
– Needs to be run on the final application
• Implemented in InstaSPIN-MOTION GUI &
InstaSPIN-MOTION Lab 5c
Accuracy of Estimated Inertia
The inertia result is highly repeatable, the maximum and
minimum values for these 100 tests are within 0.5% of the mean
Tolerance of Inertia Error
SpinTAC Speed Controller can tolerate up to 4x
of inertia mismatch
TI Confidential - Maximum Restrictions
Estimation Process Torque
This continuous torque profile is sent to the motor, it is important to note that the
torque needs to be drive negative for this test
Estimation Process Speed
Even though we applied negative torque to the system it resulted in little to no
negative speed on the motor.
Troubleshooting Common Errors
Get Error Code:
uint16_t STVELID_getErrorID(ST_VELID_Handle)
• 2003
• 2004
Bad Estimation Value
Process Timeout
– High friction/cogging
force
– Automotive Pumps
Solution:
– Increase RampTime
– Motor Spins
• Washing Machines
Solution:
• Decrease GoalSpeed
– Motor starts slowly
• Compressors
Solution:
• Increase OutputTorque
Difficult Applications for Inertia ID
• Features of Difficult Applications
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Large Cogging Force
Large Friction
Low Rated Speed
Large Start-up Current
• Difficult Applications
– Automotive Pumps -> Large Friction
– Washing Machines -> Low Rated Speed
– Compressors -> Large Start-up Current
• User’s Guide goes into specifics for these applications
InstaSPIN-MOTION Lab 05c
• Implements SpinTAC Velocity Identify
– Identifies the system inertia
– Provides the system inertia to use with the SpinTAC Velocity
Controller