The German Aerospace Centre (DLR), in cooperation with the Harbin Institute of Technology (HIT), has already developed a robotic hand similar to a human hand – with the aid of miniature actuators and high-performance bus technology.
Constructing a robotic hand with the capabilities and dexterity of a human hand requires at least four fingers: three fingers to allow the robotic hand to grip conical parts, and a thumb used as a support. Consequently, the new robotic hand consists of three fingers, each with four joints in three degrees of freedom. The fourth finger, designed as a thumb, has four degrees of freedom. It goes without saying, that the diverse movements made possible by this solution have to be controlled and monitored in a practical manner. Within this context, high-performance information channels are an essential function of the control system, particularly when performing intricate tasks. Therefore, along side high-volume processing, time is of the essence. The real time-capable 25 Mbps highspeed bus is incorporated in the robotic hand itself and developed specifically for this application.
Bus technologies for the “nerves”In the past, robotic fingers were moved using cable pulls. In contrast, modern-day microengineering allows the motor to be fitted directly in the finger. In this case, supplying the control processor with the requisite position and operating data. This is an integral part of the overall operation – and the only way of allowing the actuator to use its strengths to the fullest. Each finger joint features a company-designed contactless angle sensor as well as a torque sensor. Since both sensors require an extremely high resolution, a bus is used to transfer the wealth of data required. Rapid feedback for comparison of setpoint and actual value is crucial to the based on FPGAs (Field Programmable Gate Arrays). Only three leads are required for the external serial connection from hand to control processor.
The actual control system, a signal processor on a plug-in PCI card, is integrated in a standard PC. An operator-friendly interface allows the “hand” to be controlled from the computer. All sensor data can be displayed on the monitor. Data display, control and the connection of hand to computer were designed, from the outset, with a view to future use in industrial environments. Besides the “nerves” and the “brain”, a functioning hand also requires “muscles" to give it strength.