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CiA 402 servos in medical devices

GE Healthcare (USA) uses the MCM CANopen motion controller by Servotronix (Israel) in several medical devices. The servo controller replaces six separate components, fitting them in one module controlling multiple axes.

GE HEALTHCARE WAS LOOKING TO DEVELOP the next generation of their Discovery 600 series. In order to increase the lifetime of their parts, the engineers wanted to move from brush-based technology to the more durable yet harder to control brushless technology. In addition, the medical device manufacturer wanted to reduce their production costs, to increase the accuracy and smooth operation of the system, and to reduce the footprint of the control systems.

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Servotronix was selected among several vendors. The company, CiA member since 2010, developed the MCM all-in-one motion control module. It substitutes the previous six-part solution (cards, 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 filters. 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. This module complies with CiA 301 (CANopen application layer) and CiA 402 (CANopen motion control profile). CiA 402 is internationally standardized in IEC 61800-7-201/301.

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, simplified the system operation and maintenance, while at the same time enhancing the available functionality. 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, the 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.

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GE uses this solution in several applications. This includes NM (nuclear medicine), CT (computed topography), PET (positron emission tomography) devices as well as patient tables. “Since time to market was extremely important for us, we needed a partner that could work closely with us. Servotronix appointed a dedicated project manager that held weekly face-to-face meetings. This intensive support approach was crucial to the success of the project,” said Ilan Levin, GE’s project manager.