EDITOR ’ S CHOICE MOTION REQUIREMENTS
PORTESCAP
How to specify a motion solution for a wheeled robot
For applications that require speed and efficiency of movement , wheeled robots can be advantageous compared to legged robots . Their simpler design can also mean lower cost and reduced maintenance . To achieve these benefits , the motion system that powers a wheeled robot must be carefully specified according to the application requirements and environment , taking into account durability , efficiency , and noise .
Pradeep Deshmane , Principal Engineer - Gearbox , R & D , Portescap , and Manoj Pujari , Lead Engineer – Product & Development , Portescap , discuss the motion requirements for wheeled robots .
A major benefit of robots is their ability to complete tasks that may be difficult or hazardous for humans to perform . Many such applications rely on wheel-driven robots . From a manufacturers perspective they ’ re easier to design , build and program . For the user , providing the terrain is not heavily obstacle-strewn , wheeled robots can be faster , more efficient , and more resilient . As such , uses for wheeled robots range from pipeline inspection to healthcare environments and even domestic use .
Integral to a wheeled robot is its motor and gearbox system . At a fundamental level , the system has to be compact and light weight and able to generate the required torque for movement across the specified environment . Frequently used in tough environments , they ’ ve also got to be highly durable . For many applications , whether military surveillance or in a hospital , noise emissions must also be minimal . Critically , wheeled robots also require high energy efficiency with a low current consumption .
For these reasons , coreless brushed or brushless DC motors coupled with compact planetary gearboxes are frequently specified . As the motion system is required to fit within a footprint of less than 40 mm diameter , mini motors and gearboxes are required . Despite the compact size , the gearbox output torque must typically handle 4 to 8 Nm at speeds between 50 to 150 rpm .
SPECIFYING THE MOTION SOLUTION To determine the specification , start by calculating the output torque required . This must factor in the desired acceleration , as well as wheel diameter and mass . Torque requirements necessary to ascend gradients or overcome obstacles must also be added to the equation and finally , friction and efficiency of travel should also be taken into account .
24 PECM Issue 54