π Working Principle Explained: How It Works

1. What is an Exoskeleton and What is its Core Function? An exoskeleton is a wearable, human-machine integrated device. It couples with a person's limbs through a mechanical structure (such as a metal or carbon fiber frame, joints, and drive mechanisms) to enhance the wearer's mobility or load-bearing capacity.

Reference 1: A. M. Dollar and H. Herr, "Lower Extremity Exoskeletons and Active Orthoses: Challenges and State-of-the-Art," in IEEE Transactions on Robotics, vol. 24, no. 1, pp. 144-158, Feb. 2008, doi: 10.1109/TRO.2008.915453.

Exoskeleton Working Logic: Sensing unit collects biological/motion signals → Control unit identifies intent and makes decisions → Power unit outputs auxiliary torque → Mechanical frame transmits force to human joints.

The system first collects the wearer's motion state in real time through sensing units (such as inertial measurement units, force/torque sensors, etc.); then, the control unit analyzes the signals based on preset algorithms (such as adaptive PID or deep learning models), identifies the user's motion intent, and calculates the required auxiliary torque; finally, the power unit (usually a brushless DC motor) outputs precise assistance according to instructions, which is transmitted to the human joints through the mechanical frame to complete the enhanced movement.

Reference 1:

H. Kazerooni, J. . -L. Racine, Lihua Huang and R. Steger, "On the Control of the Berkeley Lower Extremity Exoskeleton (BLEEX)," Proceedings of the 2005 IEEE International Conference on Robotics and Automation, Barcelona, Spain, 2005, pp. 4353-4360, doi: 10.1109/ROBOT.2005.1570790.

1. Classification of Exoskeletons: Based on function and purpose, they are mainly divided into three types: health and wellness exoskeletons, enhancement exoskeletons, and load-bearing exoskeletons.

Three products developed by Kenqing Technology perfectly showcase the differences between these three types of exoskeletons: the enhanced-Π series, the health-enhancing-H series, and the load-bearing-P series.

Taking the enhanced exoskeleton Π as an example, Π adopts an innovative detachable modular design, which not only allows users to flexibly adjust the structure according to the usage scenario, but also greatly simplifies the maintenance and upgrade process. The entire machine weighs only 1.8kg, a lightweight design that significantly reduces the user's physical burden and better meets the basic requirements of ergonomics and motion assistive devices.

Reference 1: Y. Li et al., "Key Technologies of Lower Limb Power-Assisted Exoskeleton Robots: A Review," 2021 6th International Conference on Control, Robotics and Cybernetics (CRC), Shanghai, China, 2021, pp. 25-31, doi: 10.1109/CRC52766.2021.9620147.

2. Technical Selection Considerations for Commercial Exoskeletons

a) Lightweighting

A prerequisite for the use of enhanced exoskeletons is that, as experiments have shown, the exoskeleton's weight directly translates into an additional energy burden for the user. If the device is poorly designed and excessively bulky, its energy consumption may even exceed the assistance it provides, ultimately leading to a "negative benefit." Therefore, achieving net energy savings is the gold standard for exoskeleton design, which first requires the device to be sufficiently lightweight.

Reference 1: Browning RC, Modica JR, Kram R, Goswami A. The effects of adding mass to the legs on the energetics and biomechanics of walking. Med Sci Sports Exerc. 2007 Mar;39(3):515-25. doi: 10.1249/mss.0b013e31802b3562. PMID: 17473778.

Reference 2: Griffin TM, Roberts TJ, Kram R. Metabolic cost of generating muscular force in human walking: insights from load-carrying and speed experiments. J Appl Physiol (1985). 2003 Jul;95(1):172-83. doi: 10.1152/japplphysiol.00944.2002. PMID: 12794096.

b) Assisted Effects

Precise hip joint torque assistance can effectively reduce the overall metabolic cost of walking. Research data shows that using an exoskeleton for walking can achieve a net metabolic reduction of 13.6 ± 3.2% compared to not using an exoskeleton, a direct quantitative manifestation of energy savings. This energy saving further translates into improvements in key physiological indicators: on the one hand, peak heart rate during exercise can be reduced by 15%-30%, alleviating the burden on the cardiovascular system; on the other hand, by optimizing overall lower limb dynamics, it can indirectly and significantly alleviate knee joint pressure during gait, providing joint protection. Simultaneously, studies have indicated that when walking with an optimized hip exoskeleton, the user's key thigh muscle activity decreased by an average of approximately 33.6%. This intuitively demonstrates that external force intervention successfully reduces the "pulling" of muscles on the knee, thereby reducing intra-articular stress and achieving the effect of protecting the knee joint.

Reference 1: Lim B, Choi B, Roh C, Lee J, Kim YJ, Lee Y. Ultra-lightweight robotic hip exoskeleton with anti-phase torque symmetry for enhanced walking efficiency. Sci Rep. 2025 Mar 29;15(1):10850. doi: 10.1038/s41598-025-95599-2. PMID: 40158016; PMCID: PMC11954954.

c) Stable Assistance: Excellent Wearing Experience, No Shaking

Stable assistance is a key prerequisite for the practical application of exoskeletons. Unstable assistance interferes with the user's natural gait, increases control burden and energy consumption, and may even pose safety risks. Stable assistance should precisely integrate with the body's own gravitational reaction force (GRF) line to form a predictable and efficient propulsive force, rather than generating interfering torques (i.e., parasitic torque) that cause deviation or torsion.

Single-motor architecture has an inherent advantage in achieving stable assistance. Taking the structure used in the Π6 as an example, its single core motor distributes power to both legs through physically symmetrical transmission mechanisms (such as ropes and linkages), fundamentally ensuring the symmetry, timing synchronization, and consistent direction of the force lines of assistance on both sides. This mechanical symmetry makes it easy for its assistance to integrate with the GRF line, reducing parasitic torque to an extremely low level and achieving a stable "zero-torsion" pushing sensation.

In contrast, the dual-motor architecture requires complex sensors and algorithms to achieve real-time synchronization of the two independent force sources. Maintaining perfect alignment of force lines during dynamic walking is extremely challenging engineering and more prone to generating minute asymmetric forces, resulting in parasitic torque. However, this independent drive characteristic allows for differentiated and customized performance for the left and right legs.

With its assistance, it perfectly meets the rehabilitation training needs of users with hemiplegia, muscle imbalance, and other common conditions in the health and wellness market, and therefore has greater application potential in the rehabilitation field.

d) Assisting Nature

The core requirement for the practical application of exoskeletons is a natural, assisted experience. Stiff or delayed assistance disrupts the user's rhythm, increases cognitive and physical burden, and negates its auxiliary value. Ideal assistance should seamlessly integrate into the user's gait cycle, like an extension of bodily instinct, achieving a smooth "human-machine integration."

The key to achieving this goal lies in the algorithm's real-time learning and adaptation to the human body. New-generation products like the Kenchi Technology Π6, equipped with AI learning algorithms, continuously analyze the user's gait characteristics, force patterns, and real-time physical condition through multi-dimensional sensors, dynamically adjusting the assistance curve. To further enhance predictive capabilities, the system also integrates AI terrain vision. The front camera can detect road slope, obstacles, and unevenness in advance, achieving millisecond-level prediction in approximately 30ms, combined with algorithms. This means that assistance adjustments can precede the body's actual muscle responses to terrain, making the assistance not only conform to the human body but also proactively adapt to environmental changes, ultimately achieving a natural experience upgrade from "passive response" to "active collaboration."

e) Terrain Recognition

Taking Kenqing Technology's Π6 exoskeleton as an example, its significant advancement lies in the introduction of environmental perception and scene-based decision-making capabilities. The system integrates an AI terrain vision module, capable of detecting and analyzing the geometric features of the road surface in real time, such as stair steps, ramp slopes, and ground flatness.

Based on terrain recognition, the system can proactively activate matching assistance modes, rather than simply responding to human movement. For example, when detecting upward movement up stairs, it employs a torque curve that emphasizes upward propulsion; when descending a slope, it switches to a mode primarily focused on improving stability. This is equivalent to expanding a fixed assistance strategy into a set of multi-mode assistance strategies that can be dynamically activated based on the terrain. This also means that the exoskeleton's working method has shifted from passive response to proactive adaptation. In complex road conditions, users can experience the system's proactive response to terrain changes, thereby reducing sudden adjustments and cognitive load during movement, and improving the continuity and overall efficiency of long-distance walking.

f) Energy Saving and Long Battery Life

The battery life of exoskeletons is key to their practical application. There are two main ways to improve battery life: optimizing energy consumption and recovering energy.

The core of optimizing energy consumption lies in ensuring the motor always operates within its efficient range. Traditional motors, at low speeds and high currents, lose a significant amount of energy due to coil resistance heating – known as "copper loss." High-KV motors, however, can respond quickly even at low voltages, perfectly matching the user's walking frequency and avoiding inefficient idling. Combined with a precise low-resistance winding design, the overall heat dissipation is extremely low, with almost all electrical energy used for work rather than being lost to the air.

Recovering energy is another breakthrough. During downhill sections, deceleration, or passive swaying, the motor instantly switches to generator mode, converting the kinetic energy of the limbs back into electrical energy to recharge the battery, achieving "charging while walking."

Kenqing Technology's Π series products represent the culmination of the aforementioned solutions: by employing a high-KV motor and a single-power structure, they reduce basic energy consumption at the source, while integrating energy recovery functionality. This systematically improves endurance from both structural and energy perspectives, allowing for all-weather, weight-bearing assistance with just a small battery.

Reference: Ren, L., Cong, M., Zhang, W., & Tan, Y. (2021). Harvesting the negative work of an active exoskeleton robot to extend its operating duration. Energy Conversion and Management, 245, vp. https://doi.org/10.1016/j.enconman.2021.114640

e) Body Adaptability, Flexible Fit, and Comfortable Wear

Body adaptation for exoskeletons is a common challenge: providing sufficient support while accommodating differences in height and limb length. Currently, there are two main solutions:

One is the traditional dual-sided rigid frame, providing support through rigid structures in the waist and legs. Its advantage is stability and strength, but it restricts body movement and has strict requirements on body size.

The other is an adjustable modular design, with multiple adjustment points in key areas, accommodating a wider range of body types, but the overall design is still limited by the frame's shape.

In contrast, reducing rigid connections and making the structure more flexible is considered a more promising direction. This can better adapt to different body types and activity postures while maintaining support functionality. Kenqing Technology's Π plus exoskeleton adopts this approach, eliminating the rigid waist and side frames of traditional designs, reducing the wearer's limitations during activity. It is claimed that this design can accommodate a wide range of heights, including a special body type of approximately 2.16 meters tall (as tested by Shaquille O'Neal). This design attempts to provide a solution for expanding exoskeletons to more user groups of different heights and activity scenarios.