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DC Motors Make for a Powerful and Flexible Robot Arm

Micro DC Motors Pack a Powerful Punch

Robot with Powerful Arm Powered by Micro DC motorsToday, 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 maneuvering 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 micro motors have become an essential component.

For difficult, dangerous tasks, telerob, a specialist in remote handling technology, has developed the disarming robot, Teodor. The all-terrain 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 center of gravity, the manipulator arm can lift up to 66 lbs 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.

flexible robot arm driven by micro DC motors

Small, Light and Strong

Having said that, holding a 66lb mass at the end of the arm securely poses quite a challenge. At the same time, specific tasks call for precision rather than brawn. 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 micro motor 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 micro DC motors with planetary gearheads and holding brakes. The 3557 series motors perform up to 26W at rated voltages of between 6V and 48V. Together with the preset gears of series 38/2, they can develop forces up to 10 Nm. The all-metal 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. The compact unit can be exchanged rapidly - for maintenance purposes or if it has been damaged. Another key advantage: the robust brush DC 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 to the wrist.

Compact drive units made of precision DC 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.

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