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 (in the 20-21 kHz range). This field provides a spatial reference frame, referred to as “Coil Pro frame”, 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 extract the data required for positioning in the Coil Pro frame. No manual pairing or connection step is required.

SDK compatibility note: The Rokoko SDK supports Smartgloves (both generations). The Smartsuit Pro II has no Coil Pro compatibility via the SDK.

Smartgloves: IMU + EMF Sensor Fusion

Smartgloves combine complementary sensing technologies:

• Inertial Measurement Unit - IMU (SGI & SGII): Measures linear 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.
• Electromagnetic Field receivers - EMF(SGI & SGII): Serve a dual purpose. When a Coil Pro is used, the arm sensor detects the Coil Pro’s magnetic field to calculate the Smartglove’s absolute position within Coil Pro frame. The finger sensors and arm sensor also detect the smaller transmitter coil located on the hub of the Smartgloves itself, which provides accurate finger and wrist positioning.
• Magnetometer (SGII): A 3-axis magnetic field sensor on the hub. It samples the ambient geomagnetic field to provide a heading reference - correcting IMU drift over time. The magnetometer is susceptible to local magnetic disturbances (nearby ferrous materials, motors, or metallic structures).

Position and orientation data for the sensors are estimated through sensor fusion of all inputs, combining the stability and global reference of EMF positioning with the responsiveness of IMU data.

EMF component 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 pose calculations.

The field strength diminishes by the inverse cube of the distance from the Coil Pro.

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 pose 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
• Operate outside the saturation zone (the near-field region immediately around the Coil Pro, approximately 50cm from the centre of the Coil Pro) where the field saturates the receiver, so measurements are corrupted.