The Robotics of Exoskeletons

Exoskeletons are devices that can be applied to the human body for rehabilitation or motion assistance purposes.

The development of biomedical exoskeletons was for the purpose of assisting those with permanent, temporary, or partial immobility, whereas industrial exoskeletons have been designed to assist with physical activities of prolonged duration or redundancy.

Within an exoskeleton, motors, sensors and servo drives act as components of the human body. Celera Motion can help decrease time-to-market as the single supplier for all precision motion component requirements.

The Challenge

As wearable robotic devices, exoskeletons work by aiding the recovery of user mobility or stabilizing limbs for extra assistance in order to reduce fatigue and minimize injury. The result is additional strength or the replacing of muscle function for human motion.

Exoskeletons can be powered in many ways, but most frequently are mechanically, electrically, or hydraulically driven. The ‘nervous system’ of the exoskeleton, or in this case the servo drives, direct the movement of the motors as the human brain does with muscles – the encoders monitor and respond to the motion.

It is a challenging task to design bio-compatible, wearable machines that conform to the contours of the human body. Exoskeleton devices must be light, compact and reliable while offering a comfortable, wearable solution.

The Robotics of Exoskeletons

Image Credit: Celera Motion

Types of exoskeletons:

  • Biomedical exoskeletons
  • Industrial exoskeletons
  • Military exoskeletons

Biomedical exoskeletons are primarily designed for the purpose of motion assistance or rehabilitation. These devices assist people who encounter constant, or temporary, partial immobility.

Industrial exoskeletons are manufactured to aid workers in performing demanding physical activities of prolonged duration or excessively redundant tasks, such as assembly line manufacturing work.

Some manufacturers even mandate that exoskeletons are compulsorily personal protective equipment (PPE) for distinctive tasks – advancing productivity and safety.

The Robotics of Exoskeletons

Image Credit: Celera Motion

The Solution

Celera Motion combines high torque density motors, ultra-small servo drives and precision encoders, making the company the prime choice of partner for the supply of components and sub-system solutions.

The low-profile Capitan Series servo drives can minimize the overall height of a joint, allowing the design to be flat, reducing overall weight while maintaining excellent performance. These features allow the exoskeletons to be flexible and compact for enhanced wearability.

Design flexibility is also enhanced due to the integration of ultra-flat Omni+ Series motors, allowing users to experience exceptionally high torque density, with large rotor ID to stator OD ratios. Depending on the final application of the exoskeleton, two distinct encoder technologies can be regarded: absolute optical or inductive.

Aura Series absolute optical encoders offer the highest degree of accuracy across an extremely small envelope, primarily used in clean environments for biomedical exoskeletons.

The Mini Ultra IncOder Series inductive encoders are durable and can be relied upon for operation in harsh and challenging environments, such as industrial exoskeletons. These components facilitate compact, reliable, powerful and precise motion control.

The Robotics of Exoskeletons

Image Credit: Celera Motion

The Benefit

As exoskeletons are worn on the human body, it is crucial that the robot’s overall temperature needs to remains low and stable. The Capitan servo drive’s extremely low heat generation means that it is possible for the robot to remain wearable at all times.

At just 10.3 mm tall, the tiny servo drive provides an RMS current of 10 A, with a PWM commutation frequency up to 200 kHz. With a standby power consumption of only 1.2 W, it is the optimal solution for battery-powered devices. For tight integration, the drives are inherently compatible with the Omni+ Series motors, designed with thin cross-section form factors.

The ultra-small Aura Series absolute optical encoder is just 9 x 7 mm in size – with an accuracy of ± 0.01°. The Mini Ultra IncOder inductive encoder is available in 37 mm diameter, and has been developed with a through-hole for easy routing of cables or other system elements. This encoder is durable and dependable, offering resolution up to 20 bits.

Reduce your time-to-market with Celera Motion – the single supplier for all precision motion needs.


Capitan Series Servo Drives

Table 1. Source: Celera Motion

  Capitan XCR Capitan NET Capitan CORE
Continuous Current 10 A 10 A 10 A
Standby Power
1.5 to 2.1 W 1.28 W 1.12 W
Weight 38 g 18 g 18 g
Dimensions 42 x 29 x 9.4 mm 34.5 x 26 x 10.3 mm 34.5 x 26 x 10.3 mm
PWM Switching
20, 50, 100, 200 kHz 20, 50, 100, 200 kHz 20, 50, 100, 200 kHz


Omni+ Series Motors

Table 2. Source: Celera Motion

  60 mm 70 mm
KtTRAP* Up to 0.353 Nm/ADC Up to 0.507 Nm/ADC
KtSINE Up to 0.306 Nm/Apeak Up to 0.439 Nm/Apeak
Through Hole 31 mm (Rotor ID) 38 mm (Rotor ID)
Continuous Torque 0.41 to 1.26 Nm 0.51 to 1.56 Nm
Peak Torque 1.2 to 4.94 Nm 1.43 to 5.79 Nm
Rated Speed at 24 V Up to 7,000 rpm Up to 7,000 rmp

* Winding dependent

Aura Series Absolute Optical Encoders

Table 3. Source: Celera Motion

. .
Accuracy ± 0.01°
Repeatability ± 1 LSB
Operating Temperature -20 to 85°C
Weight 1.5 g
Dimensions 9.0 x 7.0 x 1.2 mm


Mini Ultra IncOder Series Inductive Encoders

Table 4. Source: Celera Motion

. .
Accuracy ≤75 arc-seconds (depending on size)
Resolution Options Up to 20 bits
Operating Temperature -60 to 105°C
Dimensions 37 and 58 mm (OD), 5 to 12.7 mm (ID)


All specifications subject to change.

This information has been sourced, reviewed and adapted from materials provided by Celera Motion.

For more information on this source, please visit Celera Motion.


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