World Walking Day丨With exoskeletons, they can walk again!

Produced by: Science Popularization China

Author: Chen Danhui (Institute of Intelligent Machinery, Hefei Institutes of Physical Science, Chinese Academy of Sciences)

Producer: China Science Expo

September 29th of every year is World Walking Day. However, not all groups can have the experience of walking whenever they want. For the elderly and people with physical disabilities, walking normally like ordinary people is a luxury. Technology provides these people with the right to walk.

Make up for the demand gap and turn "no" into "walking"

According to the latest population data released by the National Bureau of Statistics, by 2022, the number of people over 60 years old in China will reach 280 million, accounting for 19.8% of the national population. China is one of the high-incidence areas of stroke , and about 70%-80% of the survivors have varying degrees of physical disability.

Elderly people with limited mobility

(Photo source: Veer Gallery)

In addition, there are also a large number of patients with limb injuries caused by accidents. According to the 2021 Statistical Bulletin on the Development of Disability Affairs, there are 4.07 million people with limb disabilities , the largest number compared to people with other disabilities.

The large number of people with physical disabilities in my country has led to a huge gap in the supply of rehabilitation medical equipment.

In order to provide better rehabilitation services for the elderly and physically disabled patients with limited mobility, China's rehabilitation experts and researchers are trying to use intelligent technology to help these groups with their daily travel. The lower limb exoskeleton walking robot developed by the Advanced Manufacturing Center of the Institute of Mechanical Intelligence, Hefei Institutes of Physical Science, Chinese Academy of Sciences, is one of the achievements of rehabilitation medical equipment.

The lower limb exoskeleton walking robot is a typical human-machine integrated system worn on the operator's lower limbs. It integrates robot technologies such as bionic mechanisms, sensor information detection and fusion, human intention recognition and coordinated control, and organically combines the operator's intelligence and the robot's "physical strength" .

This device is mainly used to assist patients with stroke, spinal injury and the elderly, and can help them achieve typical movement gaits such as walking on flat ground, going up and down stairs, taking balanced steps on the spot, and crossing obstacles.

Human-machine combination, walking is not tiring

In early 2014, the Advanced Manufacturing Center of the Institute of Mechanical Intelligence, Hefei Institutes of Physical Science, Chinese Academy of Sciences, independently developed a lower limb exoskeleton, which has been continuously improved and perfected, and the prototype has been put into hospitals for further testing and trial use. Today, the lower limb exoskeleton walking robot is in the initial stage of application.

Prototype for helping the elderly and disabled

(Image source: author)

This exoskeleton is an active system . The control system is based on an integrated design concept and establishes an exoskeleton robot distributed control system architecture based on the CAN bus (a serial communication protocol bus for real-time applications that can use twisted pair cables to transmit signals and is one of the most widely used field buses in the world) to achieve efficient and reliable control of the robot. The device generates the required power through motor drive. For example, if the hip joint cannot move or the knee joint is weak, the motor outputs the appropriate power after calculation.

The drive unit is placed in the exoskeleton system. The mechanical design of the exoskeleton is also based on an integrated architecture and modular design concept. The overall architecture of the two types of robots, assisting the disabled and assisting the elderly, is the same, except that the degrees of freedom configuration of the hip and ankle joints are different .

When the robot is used to assist , its hip and ankle joints are configured consistent with the human body's degrees of freedom. In addition to the active degrees of freedom, the hip joint has two passive degrees of freedom, and the ankle is also configured with two passive degrees of freedom. When the robot is used to assist the disabled, the hip and ankle joints of the disabled patients have lost their active driving capabilities, so the passive degrees of freedom of the hip and ankle joints are cancelled.

The figure below shows the wearable diagram of the two types of robots, the overall virtual prototype and the virtual prototype of the hip and ankle joints more intuitively.

Virtual prototype of a robot that helps the elderly (or the disabled)

(Image source: The research project team)

The entire robot is divided into multiple modules, including the left leg exoskeleton, right leg exoskeleton, back frame, chest strap, controller, power supply and backpack. Quick disassembly and assembly interfaces are designed between the modules to enable the exoskeleton system to be quickly put on and taken off. At the same time, it can be folded during transportation to effectively reduce the occupied space.

Since the lower limb exoskeleton walking robot needs to coordinate movement with the human body, the exoskeleton robot and the wearer form a human-machine system . In order to achieve the purpose of coordinated movement, in addition to accurate intention recognition, it is also necessary to build an effective interaction channel, control loop and control algorithm to achieve the coordinated unification of human-machine movement.

The architecture of the human-machine coordinated control system is shown in the figure below. The internal mechanism of human-machine interaction can be explained by two interactive channels: intention recognition and robot motion output . Through these two interactive channels, the robot accurately and in real time obtains the human body's motion intention, and the robot acts on the human body according to the designed control, thereby achieving coordinated and unified human-machine interaction.

Human-machine coordinated control system architecture diagram

(Image source: author)

Conclusion

With the continuous improvement of my country's scientific and technological strength, major breakthroughs have been made in key components such as motors, harmonic reducers, servo drives, and torque sensors, providing a strong foundation for the independent research and development of lower limb walking robots. With the dedicated research, collective wisdom, and solidarity of scientific researchers, I believe that in the near future, people with physical disabilities or inconvenient legs and feet will also be able to "walk briskly"!