To effectively develop an improved system for radiation treatment, our customer tasked our team of engineers with pushing the limits of compact linear motor and encoder assembly. Our team delivered by providing a custom assembly of linear motors acting upon seven axes with two sets of seven encoders relaying data, all within a 1.5-inch housing.

The Challenge

Radiotherapy cancer treatments can be more effectively delivered with high resolution, high speed beam collimation. Shaping the beam is critical to deliver more focused treatment of tumors at destinations within the body. To achieve the necessary beam shaping, the customer required a new system capable of highly precise motion of seven parallel axes in a space just 1.5 inches wide. This solution needed to include a linear motor and two encoders per axis for safety and redundancy.

The Solution

Starting with the customer’s payload and move profile, Celera Motion developed a set of custom Javelin™ Series linear motor assemblies that fit seven axes in the customer’s extremely small 1.5 inch housing. In parallel, Celera Motion worked with the customer to develop a custom linear scale and interface card that allowed the customer to get position data from two sets of seven ChipEncoder™ Series encoders out of one connector and cable. Each axes was designed with a completely redundant feedback system.

The Benefit

Close collaboration between the customer and the Celera Motion team produced a complete, highly integrated motion and beam collimation mechatronic assembly. The resulting design was highly optimized for size and weight, which lowered the payload the rest of the system has to carry as well as helping minimize the size of the doctor manipulated end increasing the patients overall comfort during the procedure. The entire assembly was integrated and tested by Celera Motion and delivered to the customer ready to install in their new radiation therapy system.


Number of Axes7
Stator Dimensions2.2” x 1.8” x .18
Maximum Speed0.5m/s
Moving Mass0.16 kg
Low Profile< 2 mm
Close Spacing1 mm between motor sets
Smooth MotionAir core technology for sinusoidal torque output with angle and good linearity
Dynamic ResponseLow electrical time constant for high bandwidth
High AccuracyWhen used with ChipEncoder™ encoders motors operate with precision
Cogging TorqueZERO
ConstructionModular and highly integrated with customer mechanical cluster assembly
Resolutionup to 1 micron
Accuracy+/- 1 micron
Position Redundancy2 complete feedback systems per axis