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Low Cost Automation Tutorial

#037 Motion Mechanism Design - 7 : Sensor Usages - 1

Category : Drive mechanism design
April 9, 2010

Sensor usages for motion mechanism designs will be explained based on an application example diagram [Fig.1]


(1) Sensor application example in LCA

This simple automation system example with two motors produces: 1. Positioning, and 2. Pressing

1. A single axis positioning table composed of slide guides and a ballscrew.
2. A press mechanism with a cam & link converting rotary motion to up and down reciprocation motion.

(2) Sensor's role

Sensors are detectors of various physical and environmental conditions such as machine speed, position, contact pressure as information. The detected information would enable the automation system to be controlled.


In the example of [Fig.1], a non-contacting photo sensor is used each on the table position and the cam shaft's rotation angle. The sequence program operates based on the position signals from the sensors.

(3) Stepper motor and positioning sensor configuration

The example of [Fig.1] uses a stepper motor as the actuator. Since the stepper motor can be controlled for rotation angles and speeds independently, purposes of the sensors in [FIG.1] are as follows.

1. End of travel limits as overrun prevention sensors.
2. Home position signal output for positioning control.

There are three table control sensors provided in [Fig.1]. Two of which are for end-of-travel limits as overrun sensors, and the one in between is the home position sensor. The rotation angle of the cam shaft is detected with a combination of a slotted disc and a photo-micro sensor.