Encoders are critical motion control components that provide feedback on a system’s position and speed. They are used in almost every industry — such as aerospace, robotics, packaging, and textiles — and are building traction in virtual reality (VR) treadmills.
VR treadmills let users physically move in real-life space while navigating virtual environments. But unlike exercise treadmills that move in one direction and dictate the user’s speed, VR treadmills must respond to the user’s varying speed and position. In virtual environments, the user is in control, and the treadmill needs to adjust without knowing the user’s next move, which could be in any direction.
The world’s first and only commercially viable omnidirectional VR treadmill debuted in 2018 when Infinadeck provided Warner Brothers Studios with a prototype for the Stephen Spielberg movie “Ready Player One.”
The omnidirectional treadmill is located on a deck atop a stationary platform and allows the user to walk in any direction. Among more than 5,000 parts that make up the Infinadeck system, two absolute rotary encoders provide critical feedback for motion control.
In the fully closed-loop system, motion control is based on an X-Y coordinate system. The X-axis consists of various bridges, and the Y-axis uses a continuous belt. SANYO DENKI amplifiers and motors drive the system, and the two HEIDENHAIN ECI 1118 absolute rotary encoders on the motors and walking surface tell the system exactly how the surface is moving. “These are important because they help control the system’s X and Y movements, as the encoders provide the system position feedback on each axis,” said Benjamin Freeman, Infinadeck COO.
The ECI encoders feature high ruggedness and reliability in a compact, small-diameter design, making them a good fit for Infinadeck’s tight space constraints. The encoders’ blind hollow shaft directly couples to the system’s mating shaft for optimal rigidity. Their inductive scanning principle is particularly tolerant of contamination and vibrational loads of up to 400 m/sec² on the stator and 600 m/sec² on the rotor.
Rotary encoders from this HEIDENHAIN series provide positioning accuracy of ± 120 arcsec and 524,288 positions per revolution, or up to 65,536 revolutions with the multiturn version. This series also offers functional safety and a safe mechanical connection. Once integrated into an application with up to safety integrity level (SIL) 3, they minimize malfunctions and facilitate the safe operation of machines and systems.
Information from the rotary encoders and a virtual-position tracker located on the user’s back is delivered to Infinadeck’s control loop software, which manages the calculations for user position and speed to keep the user balanced and walking naturally in any direction.
The omnidirectional VR treadmill has already ventured into healthcare applications, such as Khymeia’s “Moonwalker” for neurological rehabilitation, and suggests applications for VR in defense and government, training, research and education, fitness, and — of course — gaming.
“Infinadeck’s platform is ground-breaking for the VR landscape, and we’re proud to be a part of this exciting motion control endeavor,” said Jonathan Dougherty, HEIDENHAIN’s Business Development Manager of the Automation Division.
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