Continuously Correcting for Stop In Position Accuracy
The CLPC is used to control a Posidyne Clutch Brake on cycling applications where very accurate stopping position is critical. Often when using a clutch brake in this application a limit switch or PLC is used to set the stop position. Because the Posidyne Clutch Brake with Oil Shear Technology is very consistent running steady, this works fairly well. However, as with any clutch brake unit changes in temperature, cold start to hot run and other variables cause the stopping to be shorter or longer, thereby overshooting or undershooting the desired position. The CLPC corrects for this.
How they work.
The original CLPC was designed to control high cycle applications where the scan time of PLC’s was too slow for accurate positioning. It consists of the CLPC control unit and a position encoder mounted on the clutch brake output shaft. The optical encoder counts pulses back to the CLPC control. The control is then programmed via push buttons on the face of the control to index (when given a start signal) the desired number of pulses for a complete index. Because a brake will not stop the drive instantly the brake must be engaged before the stop position allowing time for the drive to decelerate to stop. This is called the “trigger point”. When first starting the drive the index distance is programmed into the control and the trigger point is set automatically. As the drive is indexed, if the stop is out of position, the trigger point automatically adjusts until the stop is in location. This typically works on a 5 index algorithm to avoid hunting. When the correct number of pulses is reached (the trigger point) the control will signal the brake to engage and release the clutch. The stop position can be adjusted by using the manual adjust setting to adjust the stop position 1 pulse at a time to the desired position. This then becomes the stop or home position. When the brake signal is received and the brake is engaged it will decal to stop within so many pulses. In operation any variation in stopping due to temperature change or load change, or torque change will cause the stop to be out of position. The trigger point (count when the brake is signaled to engage) will then be adjusted to compensate for the error. This is done on a 5 count algorithm to avoid “hunting”. The result is the trigger point continually adjust itself to maintain an accurate stopping position.
There are other features that offer benefits to the user of the CLPC LC.
Stall Detection - Detects a jam (no rotation of the encoder) before reaching the desired stop position and disengages the clutch. This would be advantageous for those applications where jams are a possibility. If the machine jams causing the clutch to slip the stall detection will time out (setting is adjustable) and stop the index. This feature will protect breaking the machine and burning up the clutch or motor.
Watch Dog Timer - disengages the clutch if the index is not completed with in the time allowed. This setting is adjustable (100 milliseconds to 1 minute) on the control. This feature is to protect against jams, clutch slipping, or other cause that slows the index below allowable thresholds.
Manual Adjust - Manually adjusting the machine stop position from the home position. This feature allows setting the stop position in the best position from the front of the control eliminating the need for moving an eye or prox. switch.
In Position Output - This feature can be adjusted to a plus and minus range that is an acceptable “in position”. This then triggers a contact that can be used to indicate to another drive that the system is in position and ready for the next operation.
The basic CLPC Control Model LCis designed to operate a standard Posidyne Clutch/Brake in an indexing application. The CLPC-LC is programmed for the desired index distance (encoder counts). The CLPC-LC will energize the clutch valve until the trigger point, de-energize the valve and stop in position. The trigger point is self compensating to actuate the brake at the proper time to consistently stop in position and will float as conditions change. The CLPC Control Model LC is a single direction single clutch drive control.
The CLPC Control Model LC has numerous features such as:
Enclosure: Aluminum/Stainless, Black anodized, NEMA 1, IP20 Enclosure. NEMA 4, IP66 when door mounted with gasket
Weight: 3.5 Lbs.
Dimensions: 6” x 6” Face x 5-3/4” Deep
Operating Temperature: 32° - 140° F (0 - 60° C)
Storage Temp Temperature: 0° - 186° F (-18° - 85° C)
Ambient Humidity 90% non-condensing max.
Vibration 2.5 g’s, 30 to 200 Hz.
Interface: All functions adjustable through display panel push buttons. Some of these Functions include:
Index Count Up to 65,535 pulses.
Manual Adjust ± 1/4 of maximum count.
Encoder Input Control x1, x2 and x4 operation.
Watch Dog Timer Off, 100 ms to 1 min. in 16 increments.
Push Buttons Five: Program, Menu Back, Menu Forward (Fault Reset), Increment and Decrement.
Optional (MIP/PLS) Multiple Indexing Parameter Groups - Capable of storing up to 16 different groups. Programmable Limit Switch - Capable of 4 Programmable Outputs based on position.
Typical CLPC LC Applications
|Assembly Line Part Conveyor
|Press Feeder - CLPC-LC
Ferris Wheel Turn Over
Part Cut-Off - CLPC-LC
The Optical Encoder provides the pulse counting system for the CLPC Closed Loop Position Control using a disc with precision holes and photo interrupters placed in the correct position. By sending a pulse when the interrupter sees the edge of a hole, an accurate count is made. Using two interrupters improves the resolution and the direction of rotation is also known. A third interrupter is used to establish a home position. The home position is used as a starting point for the count, which eliminates the possibility of accumulated error.
The (2) basic types of Optical Encoders are:
Electrical Specifications (All Optical Encoders)
Environmental Specifications (All Optical Encoders)
Mechanical Specifications (Posidyne Mounted)
Mechanical Specifications (Double C Face Mounted)