© Photo | Husqvarna

Robots at home alone

Quiet and reli­able robots do the lawn mowing and vacuum cleaning

Vacuum cleaning? Lawn mowing? Nowa­days, that is done by robots: auto­mat­i­cally, quietly, reli­ably and without grum­bling

Look who’s mowing the lawn, ask the neigh­bours as the Auto­mower® glides across the lawn, as if by magic. The blades of grass are cut to size all over, appar­ently without any recog­nis­able pattern. At the same time, a flat, prehis­toric-looking crea­ture is crawling over the parquet and carpets. The Trilo­bite leaves nothing but a dust-free floor behind as it makes its way through the apart­ment. House­hold robots are playing an ever greater role in relieving us of our chores in house and garden. This is made possible by EC tech­nology.

High perfor­mance in a small space

An extinct arthropod from prehis­toric times inspired Elec­trolux to develop the world’s first fully auto­matic vacuum cleaner, the Trilo­bite, at the turn of the millen­nium. Flat and as nimble as its prehis­toric name­sake, the robotic vacuum cleaner glides over the floor without colliding with anything. The fact that the floor is then sparklingly clean is made possible in part by ebm-papst.

Elec­trolux devel­oped the blower sections itself. Then the Swedish house­hold appli­ance special­ists needed a motor to match, a motor that could satisfy the rigorous demands on the aspi­rator, and which was also cost-effec­tive. “The limited space meant that the required air perfor­mance could only be achieved by using a high speed,” explains Achim Labitzke, Product Manager at ebm-papst in St. Georgen. However, for reasons of cost, only a single-phase Vari­o­drive motor was possible. This is usually employed in compact fans with a power draw of ten watts. Now it should draw 55 watts at 18 volts to generate a speed of up to 18,000 rpm. “We recon­ciled the cost aspect and the power require­ment by opti­mising the motor output and devel­oped a powerful suction drive,” explains Labitzke.

Opti­mised effi­ciency is essen­tial for good battery perfor­mance. After all, the suction drive uses two thirds of the Trilobite’s energy. The single-phase EC motor achieves an effi­ciency of 75 percent despite the high speed. This creates an overall effi­ciency of 45 percent for the blower. That is some 10 percentage points more than a mains-powered vacuum cleaner. And despite this extreme mechan­ical load, the blower motor has a service life of more than 2,000 hours.
More­over, the EC motor is by its very nature quiet. To enable the complete blower to have a maximum noise level of 75 deci­bels, addi­tional acoustic opti­mi­sa­tions were performed in St. Georgen. Now, the fully auto­matic vacuum cleaner buzzes through the apart­ment without disturbing anybody talking on the phone or watching TV.


The pioneer of robotic vacuum cleaners. The Trilo­bite works out the most effi­cient way of cleaning a room. It uses ultra­sonic waves to detect and circum­vent obsta­cles. If used regu­larly, it will reduce manual vacu­uming to about once a month.

On a knife’s edge

The auto­matic lawn­mower from Husq­varna sneaks past its hand-propelled compa­triots with a working volume of well under 64 deci­bels. But that is not the only thing the robotic vacuum cleaner has in common with the Auto­mower®. Above all the cutter drive, which is supplied by ebm-papst Land­shut, repre­sents a prime example of a product that has been opti­mised with respect to cost and perfor­mance. “At first we were not sure whether the require­ments for the new motor were maybe a bit too much,” admits Sieg­bert Hartauer from the lower Bavarian sales organ­i­sa­tion, describing the early misgiv­ings. After all, Husq­varna was counting on contin­uing its success story.

Since 1994, the Swedes have been using a single-core, brush­less direct current motor from Land­shut to turn the cutter blades in the four Auto­mower models 210 C, 220 AC and 230 ACX and solar Hybrid. Husq­varna employs a mechan­ical trick to over­come the weak start-up torque, which is the draw­back of the low priced single-core motor. The razor-sharp blades are not fixed to the rotating disk. Rather, they fold out once the working speed has been reached.

The 260 ACX was launched at the begin­ning of 2009. The largest model of the auto­matic mowers is designed for semi-profes­sional use and has a mowing range of around 6,000 square metres, so it needs a more powerful motor. Until now, the BG 3633 has been used as a fan drive in heater blowers, with a service life of up to 20,000 hours. Yet the 50 watts power output required by Husq­varna still caused the motor to over­heat. Until the engi­neers at Land­shut found the solu­tion. A modi­fied cooling blade now expels even more heat, allowing the motor to defy the greater power. Its ideal oper­ating point is at 1,750 rpm with a power output of more than 45 watts – and an effi­ciency of 63 percent. This energy effi­ciency allows the Auto­mower® to cut a lot of grass before it needs to return to the charging station. And there is another char­ac­ter­istic that links it to its vacuum cleaning compa­triot. You don’t have to persuade it to work, and it doesn’t demand any praise after­wards.


Within a limi­ta­tion cable laid out along the borders, the Auto­mower® auto­mat­i­cally carves its way over the lawn. Day or night, sun or rain, even on gradi­ents of up to 35 percent.

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