Researchers have been trying to create robotic hands for years that can grab and move items with the same dexterity as human hands. These early robotic hands, however, were not built to endure the physical pressures that may be present in chaotic conditions. A research team has now created a small robotic finger that is flexible and resilient to physical shocks in its working environment.
On October 14, 2022, a group of scientists from Harbin University of Technology (China) published their findings in the journal Frontiers of Mechanical Engineering.
Robots often operate in unexpected and sometimes dangerous conditions. When multi-fingered robotic hands are needed to operate in chaotic situations, such as those where impediments move fast or where the robot must communicate with people or other robots, physical accidents cannot be avoided.
The robotic hands’ hardware systems might be harmed by the energy these hits produce. Because the existing dexterous hands are stiff, physical impacts and collisions may easily harm them. Robots with strong, dexterous hands that can endure physical impacts are required. The study team set out to build a robotic finger with the dexterity and resilience to endure the physical shocks of the human finger.
According to Yiwei Liu, a professor at the Harbin Institute of Technology in China, “this will allow the dexterous hand to have superior mechanical resilience, thereby eliminating the issue that the rigid driven dexterous hand is readily injured by physical collisions in unstructured situations.”
Robotic hands now in use employ an actuator mechanism with variable stiffness. The dexterous capabilities of the robotic hand are made feasible by these technologies. Depending on the work at hand, the muscles’ innate stiffness and flexibility in the human body change. Depending on the job at hand, the variable stiffness actuators let the robotic hand become flexible and stiffness adjustable like a human hand.
Two actuators power the variable stiffness actuator. This necessitates the need for two sets of decelerators, actuation mechanisms, and sensors in the robotic hand system. The variable stiffness actuator is not a good option for developing the compact dexterous hand since its complexity, weight, and volume are all increased.
The research team created an antagonistic variable stiffness finger mechanism to address these issues. In comparison to the present cable-driven dexterous hands, this finger is based on gear transmission, which is often more dependable, simpler to construct, and easier to maintain. The idea of mechanical passive compliance, which regulates the contact forces between a robotic manipulator and a stiff environment, is the foundation of the mechanically robust finger.
The mechanical finger can alter its stiffness to meet the demands of the work it is doing while also being able to absorb physical blows. The benefit of this finger mechanism is that it has a very compact construction, an adjustable stiffness function, and does not need any extra actuators, which would add weight and complexity.
The team’s finger prototype weighs 480 grammes and was made using alloy material and 3D printed components. The researchers put the finger through a number of gripping and manipulation tests. To evaluate the finger’s clutching abilities, a range of common objects—cylindrical, rectangular, and spherical objects—of various sizes were employed.
In addition to being effective for strength, grabbing, and manipulation, their finger mechanism has shown to be strong in withstanding physical blows.
The team hopes to expand the finger’s range of stiffness modification in further studies, as well as make it lighter and smaller overall. The creation of a fully dexterous hand is the ultimate objective. Prof. Liu said, “This study is of considerable value to enhancing the manipulation level of dexterous hands in open settings or physical interaction activities.”
