Today, mobile robots are often deployed in critical situations that are simply too dangerous for humans to handle – as part of industrial operations, law enforcement or anti-terror measures, e.g. to identify a suspicious object or disarm a bomb.
Owing to the extreme circumstances, these "manipulator vehicles" have to meet particular requirements. Exact manoeuvring and precision handling of tools are two essential prerequisites.
Of course, the device also has to be kept as small as possible in order to allow access through narrow passageways. Naturally, the drives used for such robots have to be equally impressive. Special high-performance micromotors have become an essential component.
For difficult, dangerous tasks, telerob, a specialist in remote handling technology, has developed the disarming robot Teodor. The allterrain mobile robot on caterpillar treads is controlled wirelessly via radio. Lead gel batteries provide it with power, which makes it completely independent. Because of the low centre of gravity, the manipulator arm can lift up to 30 kg securely.
With a swivel range of 360°, it effortlessly reaches everything within the vicinity of the chassis. The telescopic module allows the arm to extend by another 400 mm, often a decisive advantage when using a particular tool or inserting a key into a lock.
Small, light and strong
Having said that, holding a 30 kg mass at the end of the arm securely poses quite a challenge. At the same time, specific tasks call for precision rather than brawn. Moreover, the tip of the arm has very limited space for components. Therefore, light and extremely compact drives are required for the gripper. To meet these challenging requirements, Telerob teamed up with micromotor specialist FAULHABER. The gripper must be able to swivel around 360°, while at the same time displaying the precision and power needed to handle a range of different tasks. Power consumption also plays a pivotal role when it comes to battery driven devices, as the higher the drive efficiency, the longer the period over which it can be used.
The "drive problem" was solved by using DC micromotors with planetary gears and holding brakes. The 3557 series motors perform up to 26 W at rated voltages of between 6 and 48 V. Together with the preset gears of series 38/2, they can develop forces up to 10 Nm. The allmetal gear is durable and insensitive to brief load peaks.
The reduction ratio can be selected suitably for use between 3.7 : 1 and 1526 : 1. The compact motor gear unit fits snugly into the upper area of the manipulator arm. The integrated holding brake secures the final position in the event of a power failure. What’s more, the compact unit can be exchanged rapidly for maintenance purposes or if it has been damaged. Another key advantage: the robust DC brush motor only requires a simple control with current limit. Feedback of the current intensity via a counterpressure on the remote control lever gives the operator a feel for the force applied on the grippers or "wrist".
Compact drive units made of DC precision motors and adapted gears are ideal for a wide variety of drive tasks. They are robust, reliable and inexpensive. Staged reductions and the simple control of the motor with standard components meet all essential prerequisites for use – inexpensively, quickly and reliably.