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Motion Control Software
Dedicated Boards and Motion Control Software
When an axis exceeds maximum travel, severe damage can result. Limit switches are usually employed to alert the servocontroller of impending overtravel. In addition, the actual position of the axis reported by the motion control software can be continuously compared to predefined maximum travel values to provide secondary overtravel protection. This secondary protection is generally called motion control software travel limits. Motion control software travel limits can be used in conjunction with or in place of overtravel limit switches.
When used for overtravel protection, a motion control software travel limit is usually considered a fatal fault. As in the case of hitting hardware limit switches, the motion controller stops any movement on the axis, disables the motion control software feedback loops and the drive, and advises the host of the problem.
The limit-switch placement should allow sufficient deceleration distance between the motion control software travel limits and the overtravel limit switches. Otherwise, the system may not have enough space to stop without tripping an overtravel limit switch.
Activating an overtravel limit switch is always interpreted as a fatal fault. Here, the servocontroller must again shut down the machine. Enough travel distance must be provided beyond the overtravel limit switch for the axis to come to a complete stop without damaging the machine mechanics.
Servo following error is the axis-position error, or the difference between the commanded and actual positions, when the axis is moving. The digital servocontroller should monitor the servo following error and constantly compare it to the preset following error tolerance value. If the tolerance value is ever exceeded, the motion control software must then tell the controller to stop all axis motion, disable feedback and the servoamplifier, and notify the operator.
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Motion Control Software: AC Linear Motion Control Software Information
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