The robotic lawn mower is designed to take care of the lawn without the direct involvement of the homeowner. The principle of operation of the device seems to be simple – the robot travels on the ground and cuts the grass, however, very problematic for the designers were questions: mobile power supply and charging automation, routing, security, protection against theft. Several firms that specialize in garden tools have managed to create a completely independent machine with a range of innovative intelligent systems..
The robotic lawnmower is a complex consisting of auxiliary fittings (limiting wire and pegs), a docking station and the cutting unit itself. The machine itself resembles a traditional lawn mower, only without control knobs, the dimensions also do not differ much. Its weight on average ranges from 7-20 kilograms. There are at least two motors – to ensure the cruise and drive the cutting equipment, they are made according to the brush and brushless technology, they operate on direct current. The suspension usually consists of three / four rubberized wheels with protectors (one axle and one or two swivel wheels). But there are also biaxial products with wide slopes, which exert less pressure on the soil. Housings are made of engineering plastic (some are sealed), sometimes with rubber bumpers.
The robotic lawnmower is selected primarily in terms of performance and energy reserve. The developers have simplified the task, for each model they indicated the correct size of the site, the buyer needs to proceed from the areas that need to be serviced (from 200 to 10,000 m2). Any type of lawn can be mowed with such a mower, the only limitation is the slope, so the maximum value for some samples is 35 degrees (all robots take a height difference of 15 degrees without any problems). After the introduction of the initial settings, the car moves around the terrain chaotically. It is also possible to move along the specified routes without going through the same zones several times. At the same time, there are no missed places either, only junctions near obstacles are processed with a manual trimmer. Such a mower works economically and efficiently, keeping in memory the map of the site and its contours. An automatic lawn mower performs its functions during the day and at night, rain is also not a problem for some machines. The only thing is that manufacturers recommend stopping the machine if the ambient temperature becomes too high (45 degrees or more), since the batteries are discharged too quickly.
Obviously, the best power source for a mobile robot is a rechargeable battery, which provides absolute maneuverability. Most models are equipped with powerful lithium-ion batteries, nickel metal hydride batteries are often used. Therefore, this technique operates quietly and without exhaust gases. The time of continuous operation of various devices is on average from 40 minutes to two hours. Solar panels (Husqvarna Automower® Solar Hybrid) are a good help for maintaining energy, but not all machines have them. At a certain level of discharge of the power unit, the robot leaves for a stationary charging station, after restoring the supply of energy, it continues its route from the place where it stopped. The voltage at which the robotic lawnmower operates can be from 20 to 60 W, which determines its performance and total energy consumption (from 7 to 55 kW per month). It takes about 1 hour to mow 100 m2 area, the approximate speed of the robot is half a meter per second. The size of the equipment used directly depends on the power characteristics.
Husqvarna Automower Solar Hybrid
The working unit of the robot mower is equipped with rotary multi-blade knives, as a rule, these are 3 or 5 blades. There are machines with a double-bladed knife, shaped like a coffee grinder. In general, schemes are known with both one large cutting disc and several small ones. The cutting width ranges from 17 to 32 centimeters, of course, the larger the knife, the more powerful the motors and more capacious batteries are installed. But, for example, Robomow RL555 leaves a path 53 centimeters wide, and the knives of this mower themselves reach almost the edge of its dimensions – therefore, the edges of the designated area are better processed.
The rotation speed of the knives is quite high – several thousand revolutions. The cut grass is cut into tiny particles and spread evenly. Particles of cut grass slip between the stems and lay on the soil like mulch. They decompose at the roots in the shortest possible time, which is considered a very useful fertilizer for the lawn. The cutting height can vary from 20 to 60 mm, for this you need to use a multi-stage regulator. Too hard grass is best cut in stages, each time reducing its height. If the grass is too tall (more than 10 cm), then it is better to pre-process it with hand tools. In general, the very idea of the robot’s functioning is as follows: “mow often, but little by little.” Small objects (like cones, fruits, acorns …) cannot affect the functioning of the robot, but it is better to remove them in order to prolong the life of the knives.
The robotic mower is a smart device that needs some initial programming. First of all, along the perimeter of the site and around stationary obstacles, a special electrical cable (“limiting”, “guiding”) is installed, which is connected to the docking station. Then it is located in the form of a contour and dug into the ground or, with the help of standard pegs, is fixed in the grass. The machine picks up the electrical signal and does not go beyond the designated limits. Many lawn mowers are configured to operate in multiple cable-created zones.
Any obstacles that appear in the way are scanned by special ultrasonic sensors, then the car bypasses them, and the autonomous navigation system continues to guide the device along a pre-planned trajectory. The sensors are triggered if the robotic lawnmower is overturned, or if it is lifted (for example, by children), then the motors turn off immediately, the blades stop and there is no danger of someone getting hurt by the rotating rig. Intelligent systems monitor tilt angles, degrees of rise, the appearance of rain … For example, the Stiga Autoclip 527 detects high humidity, when it rains, it goes to the base and waits until it stops. Honda Miimo and Alpina AR2 have sensors that, depending on the thickness of the grass or the density of the cover, give a command to slow down / accelerate the movement of the knives.
The user has the opportunity to choose from the proposed mowing scenarios or create their own, depending on weather conditions, season. The movement can be chaotic, spiral (robots of the Stig brand) or parallel (a robot from the Bosch company). Operating with a timer, a person can set the daily mode of operation, duration and frequency of haircuts. Control of settings is carried out on a liquid crystal display (sometimes on signal LEDs), information is entered through a large number of buttons or menus. Some machines are offered with a remote control (Viking iMow MI 322 C). The lawn mower can be monitored using a tablet or smartphone, Bluetooth and GSM modules are standard or optional. In case of malfunctions or emergency situations, smart cars are able to send an emergency message to the specified mobile phone number.
To prevent a robot left unattended from being stolen, the developers have provided a PIN recognition system, that is, only the owner can start the mower. Also, in case of unauthorized movement, robotic lawn mowers emit a loud “anti-theft alarm” sound.
The cost of robotic lawn mowers depends on the performance and a little on the “brand” of the brand. So Gardena R40 Li, suitable for servicing 400 squares of lawn, costs about 45,000 rubles, and the price of Robomow RC302 PRD7002A is somewhere around 35 thousand (it is only charged manually and is recommended for lawns 200 m2). European middle peasants, whose prerogative is 800-1000 square meters, cost in the range of 60-65 thousand rubles, these are such items as: AL-KO Robolinho 3000, Bosch Indego, Stiga Autoclip 145 4WD. More powerful cars cost over 100,000 – for example, Husqvarna Automower 220 АС (1,800 m2). And then there is the high-tech monster Stiga AutoClip 920S, which sells for about half a million, although it is recommended for a lawn of 10,000 squares and a mow with a width of 84 centimeters..