While skylines around the world are getting taller and ever more crowded, the maintenance and repair of skyscrapers is becoming more difficult. In the absence of a friendly neighborhood Spider-Man, an aerial manipulator could help.

Traditionally, regular inspection of high-rise buildings with glass curtain walls has been conducted by humans with gondola systems, which can be very dangerous, costly and inefficient.

Chinese researchers at the Shenyang Institute of Automation (SIA) of the Chinese Academy of Sciences have designed a promising alternative. They have developed a contact aerial manipulator system that shows high flexibility and strong mission adaptability. The researchers presented their findings at the 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2019) last week in Macao.

Advancing aerial manipulation

The new robot represents a major advance in safety and efficiency, said the SIA team. It includes a single degree-of-freedom manipulator cube-frame end effector and a hex-rotor unmanned aerial vehicle (UAV).

Compared with general wall-climbing robots, the drone is capable of avoiding obstacles and even jumping over grooves on wall surfaces. The SIA team designed the aerial manipulation system so that its contact force can be controlled precisely without any force sensors.

“How to control the force is considered the most difficult problem, since flying robots usually are sensitive to external force,” said Meng Xiangdong, the robot’s designer.

Meng said realizing this objective required first making a flying robot with closed loop control behave like a regular spring system. He said that the elastic coefficient could then be easily changed by altering the control parameters.

“It means that we can take the robot as a spring system so that the contact process can be safe enough,” said Meng.

Aerial manipulator experiments and applications

The research team also conducted experiments to test the mobile manipulation system. For example, the researchers fixed a light switch to a wall, then had the robot press the switch to turn the light on and off. The robot was able to safely and smoothly operate the switch via precise force control.

In another experiment, the robot smoothly moved along a glass wall, exerting fixed pressure. The robot then used a pen attached to the end of the aerial manipulator to write “SIA” — for Shenyang Institute of Automation — on a glass wall.

“In the near future, we might see an extensive use of this new system in large infrastructure maintenance, and other special applications, such as scientific sampling.” said Meng.