With the deep integration of sensor technology, motion control, computer simulation and robot technology, the perception ability of robots in complex external environments has been significantly enhanced, and their autonomy, stability and reliability in handling practical problems have also been greatly improved. Driven by technological development and market demand, service robots are smaller in size and more flexible in interaction. Its service areas and target groups are constantly expanding and further penetrating into various application scenarios. From the perspective of development trends, service robots are advancing from "perceptual intelligence" to "cognitive intelligence". Innovation in emerging directions such as bionic robots is active, and the research and development of humanoid robots has once again achieved breakthroughs.

Bionic robots refer to robots that imitate living organisms and perform tasks with their biological characteristics. A report released by Beijing Institute of Technology and Zhongguancun Zhiyou Research Institute classifies bionic robots into three categories: humanoid robots, quadruped robots and scientific research exploration robots. Among them, humanoid robots and quadruped robots have drawn much attention from the technology industry due to the feasibility of their industrialization and application.

Recently, under the guidance of the Beijing Municipal Science and Technology Commission and the Management Committee of Zhongguancun Science and Technology Park, the "Tech Link Zhiyou Scientists' Frontier Forum - Innovation and Application of Bionic Robot Technology" hosted by Zhongguancun Zhiyou Research Institute and co-organized by the China Machinery Industry Federation and the China Robot Industry Alliance was successfully concluded in Beijing. The scientists and entrepreneurs attending the meeting engaged in divergent thinking on the current industrial status and technological research and development of intelligent bionic robots.

Three key challenges in the development of the humanoid robot industry

Humanoid robots are an advanced form of intelligent robots. They possess the physical characteristics of humans, especially with complex multi-body dynamics systems. The main feature of this robot is that it can use tools and complete various anthropomorphic tasks without changing the environment in which humans work and live. In addition, bionic robots possess human-like movement capabilities, environmental adaptability and operational capabilities. Therefore, the industry's expectations for bionic robots are: to go to places that humans cannot go and to do things that humans cannot do.

Yu Zhangguo, a professor and doctoral supervisor at the School of Mechanical and Electrical Engineering of Beijing Institute of Technology and the director of the Institute of Intelligent Robotics of Beijing Institute of Technology, believes that there are three aspects to measure the core capabilities of humanoid robots: movement ability, environmental adaptability, and multi-task operation ability. These are also the three key points that need to be broken through in the field of humanoid robots.

In terms of movement capability, domestic research institutions still need to break through the limitations of drive components and take some measures in balance control to solve the balance and stability problems of robots during movement. The movement process of bionic robots is actually a process of struggling against falling. In terms of operation, the current development of the motion capabilities and driving components of humanoid robots mainly relies on industrial assembly models. In China, the motion performance of robots is still improved through the development model of dedicated components.

In terms of environmental adaptation, humanoid robots cannot merely maintain a single movement mode such as "walking", "running", and "jumping". Instead, it should have diverse modes such as walking, jumping, and fall protection.

In terms of multi-task operation capabilities, current humanoid robots have not made significant breakthroughs in the aspect of intelligence. In the future, the industry also needs to combine the intelligence of humans and robots to enhance the ability of intelligent operation.

There are still key technical obstacles to the implementation of quadruped robots

Ji Shuting, an associate professor at Beijing University of Technology and vice president of the Intelligent Transmission Research Institute of Zhitong University of Technology, pointed out that bionic mobile robots can be widely applied in many dangerous environments such as outer space exploration, military reconnaissance, war conflicts, and disaster rescue. At present, the US military has achieved remarkable research results in the field of bionic mobile robots. They have developed bionic robot products such as fully automatic wheeled vehicles, legged robots, and exoskeleton robots for different scenarios. Countries such as Russia and Japan are also increasing their investment in the development of bionic robots.

Although the bionic mobile robot industry is booming, the economic revenue-generating capacity of this sector is not satisfactory. In 2020, Hyundai of South Korea offered 1 trillion won for the acquisition of Boston Dynamics, while seven years ago, Google paid 3 billion US dollars for the acquisition.

Boston Dynamics' technology is indeed advanced, but the main problem with the commonly seen quadruped robots at present is that in unknown unstructured terrain conditions, their stability of movement ability, load capacity, durability, manufacturing cost, and reliability still fall short compared with wheeled or tracked robots. Ji Shuting believes that the key to solving this problem lies in the joint actuator, which is the core component of the robot. Joint actuators directly determine the balance, stability and anti-interference ability of a robot's movement. At present, there are mainly three driving methods for bionic robots.

The first type is hydraulic drive. This method has a high power and strong load-bearing capacity, but it is very noisy. The second type is series elastic drive. This method involves placing an elastic element between the motor and the reducer, and using it along with an encoder to precisely measure force or torque. This method uses a relatively large transmission ratio of the reducer, but its reverse driving capability is not good. It also requires the installation of some additional sensors, which will increase its volume and weight and reduce the power density of the joint driver. The third type is semi-direct drive. The Cheetah proposed by the Massachusetts Institute of Technology adopts this model and achieves force control through the current loop scheme. This type of joint adopts a planetary gear reducer, with a transmission ratio generally lower than 10 and no additional sensors. It has a very high reverse driving capacity and gear transmission efficiency.

At present, the mainstream joint drives mostly adopt harmonic gear reducers, cycloidal gear reducers and planetary gear reducers. Among them, the transmission ratio of the harmonic reducer is generally greater than 30, with smooth transmission and light weight. It has high positioning accuracy and repeat positioning accuracy. However, the transmission efficiency of the harmonic reducer is relatively low. Compared with other reducers of the same volume, its load-bearing capacity is not high and its reverse driving capacity is relatively low. Cycloidal gear reducers are suitable for legged robots. They have stronger shock resistance, higher reliability, and the widest range of applicable transmission ratios, with corresponding higher load capacity. However, due to the high difficulty in design and manufacturing, cycloidal gear reducers are not widely used. Planetary reducers have a smaller transmission ratio, greater reverse driving capacity and higher transmission efficiency.

Ji Shuting said that currently, domestic enterprises such as the Zhitong University of Technology Research Institute are tackling the design and research and development challenges of reducers.

The future development trends of the bionic robot industry

At the forum, the "Bionic Robot Industry Report" jointly compiled by Beijing Institute of Technology and Zhongguancun Zhiyou Research Institute was officially released. Shen Haotian, a postdoctoral fellow at Beijing Institute of Technology and the Manned Space Engineering Office, introduced that the report consists of five parts and forms three core viewpoints:

First, the era of robots has arrived, and humanoid quadruped robots are a relatively promising niche market within it.

Secondly, humanoid robots bring about differentiated demands that differ from the traditional industrial robot industry chain. Compared with industrial robots, humanoid robots have more precise requirements for system components. At present, the key technical difficulties in this field are motion control, research on high-torque-density drive units, environmental perception capability, human-machine interaction capability, etc.

Thirdly, frameless torque motors and precision reducers will have more room for growth.

Regarding the fields of humanoid robots and quadruped robots, the report holds that in the future, humanoid and quadruped robots will be closely integrated with artificial intelligence. Artificial intelligence technologies represented by ChatGPT will drive the development of human-computer interaction and environmental perception technologies. Secondly, humanoid robots have put forward higher requirements in terms of perception, decision-making and control. As the industrialization expectations of humanoid robots increase, the demand for dedicated chips will also continue to rise. In addition, with the development of motor technology, direct motor drive will be the future trend of humanoid quadruped robots.

The report also pointed out that in terms of industrialization at present, humanoid and quadruped robots still face many challenges. For instance, in terms of application scenarios, the two types of machines not only need to operate efficiently in actual application scenarios but also need to address issues of stability, reliability and safety. In addition, the industry also needs to promote breakthroughs in key technologies to accelerate industrialization. In terms of scalability, the two types of robots need to be customized for special scenarios, so as to achieve the goal of adapting robots to different application scenarios.