Wednesday, 24 June 2015

Custom all-in-one Motion Control Module for Nuclear Medicine CT, PET and Patient Table.

Servotronix has developed a custom all-in-one brushless DC motion control module for GE’s NM (Nuclear Medicine) CT (Computed Tomography), PET (Positron Emission Tomography) and Patient Table. The module has replaced six separate components, fitting them in a single cost and space efficient module with a single product number for all its axes.

The Challenge

GE Healthcare was looking to develop the next generation of their Discovery 600 Series. In order to increase the lifetime of their parts, they wanted to move from brush-based technology to the more durable yet harder to control brushless technology. In addition, GE wanted to reduce their production costs, increase the accuracy and smooth operation of the system, and reduce the footprint of the control systems. As a medical device company, GE needed a solution that would conform to strict medical EMC standards.
MCM large size

Servotronix Customized Solution

Servotronix was selected among several vendors due to its extensive experience and expertise in developing customized servo drives and motion solutions, the availability of a suitable platform with an extensive array of building blocks, its ability to offer innovative engineering that would dramatically reduce GE’s production costs, and its ability to provide intensive support throughout the lifecycle of the product.

All-in-one Motion Control Module (MCM)

In the previous version, GE had six separate functions in separate cards, including tilt sensors, -filters, EMC, and GE Safety communication channel. As the application was predicted to be relatively noisy, GE needed to include a set of fi¬lters. In previous versions, these ¬filters were dispersed across the system as separate components. Servotronix consolidated all the components into a single all-in-one motion control module with a single part number. Each module was designed to be compatible with all the system’s axes, including all the axes for the detectors and the patient’s table. By combining all the cards into a relatively low cost module, GE reduced the overall cost of the system, simpli¬fied the system operation and maintenance, while at the same time enhancing the available functionality for each axis.

Velocity Ripple GraphLess than 2% velocity ripple allowing continuous scan capabilities


Absolute dual loop feedback for collision protection or smoother operation

For enhanced control, the module connects two encoders to a single axis – a preliminary feedback control is connected to the motor, while a secondary feedback control monitors the load. On every power up, MCM sends the absolute position of each axis to the host controller for collision protection to allow smooth operation and prevent any axis backlash, by reading dual feedback as shown in the diagram below.
Cradle Diagram

Conforming to medical industry standards

The control module conforms to the medical industry’s standard (Medical 60601-1-2 Class B), including conformity to electromagnetic standards (EMI/EMC). The module features an auxiliary line to monitor safety, emergency release function, and CANopen® communications interface.

Intensive support

Servotronix provided GE with intensive support throughout the project. A dedicated project manager who was appointed to manage the entire lifecycle of the product, held weekly meetings with GE personnel. Servotronix accompanied GE’s development team, providing them with the required knowledge and motion control expertise, allowing them to focus on their core capabilities.
Solution Highlights

  • Combining six separate requirements into a single Motion Control Module
  • Reduction in system components
  • Durable brushless DC technology
  • Compatible with all different axes of the NM/CT system
  • CANopen® communication interface
  • Dual loop feedback
  • Conformity to EMC/EMI standards
  • Continuous scan capabilities due to high performance and low ripple Lifecycle support
  • Allowing the customer to focus his core capabilities