Compact BXI Drives Bring Precision Motion to Robotic Joints

Faulhaber’s BXI Series introduces a compact, fully integrated drive solution designed for precision robotic joint movement. Combining a high-torque motor, optimized planetary gearhead, and high-resolution encoder into a single unit, the system delivers smooth, accurate motion in space-constrained environments. Built for seamless integration with Faulhaber controllers, the BXI platform emphasizes torque density, reliability, and simplified design, making it well-suited for robotics applications that demand precise, human-like motion and consistent performance.

The Faulhaber BXI series drive delivers tight motion control without occupying much space. Image used courtesy of Faulhaber

Functional Design

The BXI series drives are constructed from several key subsystems. Each one consists of a motor, a planetary gearhead, and a high-resolution encoder. At first glance, this is not much different than many other motor drives. However, the planetary gearhead is designed to provide maximum torque with minimal volume; torque without bulk. Planetary gearheads also ensure smooth, fast motion.

An exploded diagram of a Faulhaber planetary gearhead. Image used courtesy of Faulhaber

To ensure precision motion, the BXI series drives are fixed with a high-resolution encoder. Using a 15-bit synchronous series interface (SSI), each encoder can read up to 32,768 positions per revolution. Also, the algorithm that reads the position is resilient against interference, which can be a problem with high-resolution encoders.

The motor is designed for high torque density. The rotor has 21 pole pairs, a grooved stator, and an iron-core winding. These motors can efficiently provide up to 20 Nm of torque.

Motors, planetary gearheads, and encoders for these drives are all manufactured by Faulhaber. Instead of merely assembling components from third-party vendors, Faulhaber has engineered their components to work together to provide a low-maintenance drive unit.

BXI Series Drive Features

The BXI series drives are available in a range of voltages, up to 50 V DC. Each motor is built in a flat, corrosion-resistant aluminum case that reduces weight and helps dissipate heat away from the motor without the need for external fins or cooling fans.

The drive itself is only 34 mm long, making it suitable for tight spaces. Besides physical integration, the electronic integration is also simplified, as different BXI models are fitted with different standard industrial interfaces. Connection ports are placed on the case's flat panel so they do not interfere with the drive's motion.

Potential Applications

While the BXI series drives can be used for virtually any application requiring high-precision motion, Faulhaber specifically designed them to replicate human-like motion. Consider the tiny movements a human arm can make; an infinite number of positions in free space. The BXI series, with its 15-bit encoders, gives up to 32,768 potential positions along its axis, which is more than enough for most robotics applications.

One example case would be to use this drive as a robot’s shoulder joint. It would allow the joint to rotate through 360° and provide constant torque at all times. This is better than a human’s shoulder could do, as it is hard to manipulate objects with one's hand extended behind the back, yet this joint would allow a robot to do so.