Many customers look for systems to test their devices; to do that, they need to operate on multiple axes of motion. While there are many options for linear motion, each customer’s requirements will direct H2W to select a particular technology. A medical device company approached H2W to develop a three-axis system to simulate the motion of a patient undergoing a traumatic seizure event. This customer had issues with their current testing setup. Their existing system utilized a stepper motor translation stage, and the motor and bearing generated excessive vibration, which caused faulty readings on the accelerometer test on their device. Therefore, they required a motion system with lower vibration and the system to achieve speeds of 1.5 m/s and operate at frequencies between 0.1 Hz and 6 Hz at a displacement of 30 mm with a payload of 0.5 kg. One axis would be horizontal, the other would be a rotary axis, and the last would be a linear axis mounted to the rotary axis.
There are several options for smooth motion. A high-precision ball screw stage with a brushless motor can reduce the vibration; however, this is not an ideal solution for the speeds requested. The smoothest motion could be accomplished using an air bearing; however, this can be cost-prohibitive in many applications, and the moving cables and air lines would be complicated. Therefore, in this case, the best solution was utilizing a single rail linear motor positioning stage in X with a rotary brushless motor as the Theta and mounting another single rail linear positioning stage in Z. The linear motor allows for high-velocity motion and minimizes the complexity by only moving the cables. H2W was then able to couple this stage with a multi-axis motion controller to ensure that the frequency, displacement, and velocity requirements were all met to satisfy the customer’s requirements, allowing the ability to program specific motion patterns using time, position, and velocity parameters.
This budget-friendly solution considered the desire to have a stage capable of rapid movements without imposing vibrations that would yield faulty readings on the accelerometer. The final solution was an X-axis with 6 inches [150 mm] of travel, 1 micron of resolution, and 16.5 lbs [74 N] of continuous force. The theta-axis has limits installed to limit the travel to 180°, with a 2000 counts per revolution encoder and a continuous torque of 479 oz-in [3.4 N-m] of continuous torque. The linear axis attached to the shaft on the brushless rotary motor has 4.3 inches [110 mm] of travel, 1 micron of resolution, and 6.2 lbs [28 N] of continuous force. Thus, the customer implemented this solution to successfully test and simulate the motion while getting the readings, providing life-saving technology to those suffering from seizures.