Effective prototyping of haptic devices

Linear Resonant Actuators (LRAs) are a style of haptic motor used in many consumer electronics applications. The key features are substantially smaller thickness than other haptic/vibrating motors, lower power use, and efficient frequency changes. Most modern electronics incorporate some form of LRA. Due to spatial constraints, they are a prime choice in miniaturized applications as they can operate within a few millimeters thickness. Common applications are smart pens, smart watches, tablets, phones, and even faux-button and screen presses on many devices providing force feedback.

The design of these motors can become complicated as they are frequency driven and often the propelling force is created with an excited electromagnetic coil in a direction perpendicular to the direction of intended motion. The general setup is a tray of dense physical material with embedded magnets attached to a housing by two springs, one on either side. The tray is propelled back and forth by the coil excitation as it interacts with the magnets in combination with the restraint from the springs; eventually vibrating as required. LRAs differ greatly in design and use from the typical uneven mass, brushed, DC motors we typically see in haptic applications.

We will show that the system can be simulated with the Finite Element Analysis [FEA] using Siemens Simcenter MAGNET software, including the motion and transient packages. We will set the coil excitation, simulate the magnets and tray, and showcase the motion created from how the electromagnet forces and spring forces interact throughout a clearly defined period of time to assess performance.