Motor Solutions for Medical & Industrial Positioning Systems

Positioning systems are used in a wide variety of industries, from manufacturing, to medical, to pharmaceutical and many others.  Positioning Systems require efficient and precise movements. Coarse adjustments for high-speed positioning moves the table (or workstation) into the target vicinity, where final positioning is achieved at low speed so as not to overshoot the target position.  Once in position, the drive system must hold the position. Motion must be equally precise in both directions. Typical applications include:

• CNC tables
• AGV drives
• Surgical tables
• Radiology tables

• High speed produces heat and vibration
• Low speed fine adjustment requires precise current control
• Precision is dependent on feedback choices and electronic drive
• Gearbox reduces the motor size and provides some holding torque
• Gearbox backlash can introduce position error

Several Haydon Kerk Pittman technologies are used to design & develop positioning systems, including:

Motor with Gearbox for Coarse and Fine Motion:                           

Direct drive brush motors run best between 1000-5000 rpm. Slotted brushless motors can generally run faster or slower, but at very slow speeds, and they can experience torque ripple as final positioning settles between slots in the stator. Slotless brushless motors do not have stator slots, so fine positioning is achieved with minimal torque ripple. Slotless brushless motors are the most expensive relative to brush and slotted brushless motors. 

 

One way to mitigate torque ripple is to use a gearbox. A gearbox trades speed for torque. More revolutions on the motor translate into fewer revolutions on the gear shaft, thus providing fine positioning regardless of whether the motor stops between slots or is aligned with a slot. 

 

Encoder for Position and Velocity Feedback:                                     

Encoders provide motion feedback and are essential to precise motion. Although the drive commands the motor to move, the encoder reports how much it moved. The drive compares the command to the actual (feedback) and adjusts the motor output to achieve the set speed or position.

 

Number of encoder counts = How far it moved

Number of encoder counts per second = How fast it is moving.

 

The encoder also provides the drive with the direction based on how the signals are received. For additional details, click here.  

Brake to Hold Position when Final Position is Reached:                 

In most applications, maintaining motor power is sufficient to hold position. However, in cases such as vertical loading, with back-drivable coarse-lead screws, or with periods of long stationary times, a holding brake can be used to hold a position. Power-off brakes are closed when power is off, providing a safe and energy-efficient holding torque. If power is accidentally lost, the brake will close to prevent motion. The machine builder must decide whether the safe state allows for motion to be free (release brake) or to halt all motion (apply brake).  Most drives have an output to control whether the brake is closed or released.    

For More information on any of components used in positioning systems

Headquarters
Haydon Kerk Motion Solutions, Inc
Haydon Products Division
1500 Meriden Road
Waterbury, CT 06705 USA
+1 800 243 2715 (Toll Free)
+1 203 756 8724 (Fax)
+1 203 756 7441 (International)
info.haydonkerk@ametek.com
www.HaydonKerkPittman.com

 

Locations
Waterbury, CT
Milford, NH
Harleysville, PA
New District, Changzhou, China 
Jiuting, Shanghai, China 
Bouguenais, France 
Pegnitz, Germany 
Bangalore, India 
Suwon-city, Gyeonggi-do, Korea 
Penang, Malaysia
Reynosa, Tamaulipas, Mexico

Haydon Kerk Pittman are brands of AMETEK Advanced Motion Solutions along with Dunkermotoren, and AMETEK Dynamic Fluid Solutions.