Technology Overview: EMF, IMU, and Sensor Fusion

The Coil Pro: Electromagnetic Field Generation

The Coil Pro generates a known, stable magnetic field across three axes, operating at tightly controlled frequencies (21 kHz, 20.666 kHz, and 20.333 kHz on the X, Y, and Z axes respectively). This field provides a spatial reference frame, referred to as “coil space,” within which Smartgloves can calculate their absolute position.

The Coil Pro has no wireless connectivity. It does not use Wi-Fi, Bluetooth, or any radio communication protocol. It is a passive field generator, it does nothing beyond emitting a precisely controlled magnetic field. All intelligence, detection, and computation happens on the Smartgloves side.

When Smartgloves enter the magnetic field range, they automatically detect the Coil Pro’s presence and begin recording and computing positional data in coil space. No manual pairing or connection step is required.

SDK compatibility note: The Rokoko SDK supports Smartgloves (both generations). The Smartsuit Pro II is IMU-only and has no Coil Pro compatibility via the SDK. Coil + Suit and glove data fusion (e.g. with locomotion) is a Rokoko Studio feature and is not available through the SDK.

Smartgloves: IMU + EMF Sensor Fusion

Smartgloves combine two complementary sensing technologies:

• IMU (Inertial Measurement Unit): Measures orientation and rotational motion via accelerometers and gyroscopes. Provides high-frequency, low-latency rotation data but accumulates drift over time and has no inherent global position reference.
• EMF receivers: Serve a dual purpose. When a Coil Pro is used, the arm sensor detects the Coil Pro’s magnetic field to calculate the glove’s absolute position within coil space. The finger sensors (and arm sensor when the Coil Pro is not used in the setup) also detect the smaller transmitter coil located on the hub of the Smartgloves itself, which provides accurate finger and wrist positioning.

Position and orientation data are generated through sensor fusion of both inputs, combining the stability and global reference of EMF positioning with the responsiveness of IMU data.

Sensor layout on Smartgloves:

• The EMF transmitter is located on the hub (the component with the LED indicator)
• The EMF receivers are embedded in the finger sensors and arm sensor

Things to Be Aware of When Working with EMF

EMF-based positioning relies on a mathematical model of the magnetic field. Any physical object or device that distorts the actual field in the environment will degrade the accuracy of that model, and therefore affect positional calculations.

Common sources of interference:

• Metal objects (tables, frames, props, tripods), especially ferrous metals
• Electric motors (rigs, turntables, HVAC equipment)
• Large electronic devices in close proximity

Recommendations:

• Use plastic or wooden tables, props, and support structures where possible for best positional accuracy
• Metal objects are not a hard blocker, but their impact on accuracy is environment-and-setup-specific and should be tested in advance
• Keep the Coil Pro stationary during capture, it defines the global origin of coil space
• Operate outside the saturation zone (the near-field region immediately around the Coil Pro, approximately 50cm from the centre of the Coil Pro (Smartgloves I) and 20cm (Smartgloves II) where field geometry is non-linear and performance degrades)

The field strength diminishes by the inverse cube of the distance from the Coil Pro, which is also why there is a maximum effective range beyond which positioning is no longer reliable.