MOTORS, DRIVES & CONTROLS
SECTION TITLE
MINI MOTORS T
MERITS OF Clémence Muron on optimising compact linear motion applications with mini motors
o achieve maximum performance from a miniature linear motion application, it’s vital to make sure the motor’s specifi cation meets
the requirements. Effi ciency, high power, optimised dimensions and acceleration are among the criteria for selection to optimise demanding lead screw applications. Requirements for linear motion,
miniature applications range from fi lling syringes through to medical devices, or robotic applications used in the operating theatre. T e fi rst consideration for a design engineer is the method used to
Lead screw example
transfer the rotary motion of a miniature motor into linear motion. T e most common way of achieving this is by mounting a screw and nut system on the motor shaft. It operates on rolling contact between the nut and a screw, which can provide low friction, good effi ciency and high load capability. T e disadvantage however is the cost and the time to design such a solution, especially for applications which don’t require high load handling. A more cost-eff ective means of achieving linear motion can be reached with a standard linear motorised solution by choosing a motor with an integrated lead screw. In particular, a digital linear actuator (or DLA) utilises a can stack stepper motor combined with a screw. Inherent with stepper technology, the motor controls its own positioning and is both an accurate and cost-eff ective solution, doing away with the requirement for an additional feedback system. Resolution can be managed in full, half or micro steps. With a special optimised ball bearing assembly, the axial play can even be eliminated, improving positioning accuracy as well as repeatability of motion. In addition, with stepper technology, the
motor has a detent torque. As a result, it can hold its position when the power is removed. T e nut can be over-moulded in the rotor assembly with special material, minimising friction and consequently increasing effi ciency and lifetime. For a high-optimised linear solution, a customised package can deliver the maximal performance and characteristics most suited to the application if the motorised solution is well designed. Taking the screw section, this could include considerations over dimensions, pitch, material, ball or lead screw. Regarding the miniature motor, the can stack stepper motor can be replaced with various choices dependent on requirement. As an example, a low inertia disc magnet stepper motor ensures the highest acceleration with the benefi t of the stepper technology, providing ease of control, positioning capability and detent torque. Alternatively, a brushless DC motor maximises power density. For applications which demand energy
ABOVE: Miniature linear motion applications in the medical sector include fi lling syringes, medical devices, and robotic applications that are used in the operating theatre
www.engineerlive.com 47
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
