Robot Lawn Mower: a fast growing market
A robot lawn mower is an autonomous electric lawn mower, reducing greatly human operations. They represent the second largest group of domestic robots. Their market is still a niche but is growing extremely fast (20%), especially in Europe. Tougher grass types and cheaper lawn services limit their growth in the US. Their high prices should go down with growing volume.
A robot lawn mower uses sensors to move inside limited areas and avoid obstacles such as trees. A virtual border is drawn with wires placed around the field. Inside this boundary, the mowers use different movement patterns (planned, planned and random, planned with periodic spirals, etc.). Some can turn only in one direction (clockwise or counter-clockwise), some in both. They can handle terrains as large as 5 acres. Self-charging models go back to their docking station via radio-frequency or along a wired path. Some carry rain sensors.
Lawn Mower battery
They use different kind of batteries (NiCd, Li-ion or lead-acid). They can be charged on standard power outlets. The advantages and drawbacks of each technology is summarized in the table below. Some mowers are fully solar-powered but are less efficient and extremely costly. All the models are typically slow, at a speed around sixty feet per minute.
|Nickel Cadmium (NiCd)||Rechargeable tools||• Good service life||• High self-discharge rate
• Memory effect
|Lithium-Ion||Cell phones||• Good service life
• Constant charging capacity
• Very light
• Reasonable service life
• Better traction (weight)
• Decreasing charging capacity
They all are mulching mowers with different technologies. Light double edged mower blades preserve energy. Multiple hardened mower blades can handle quite long grass. Thin mower blades with small sharp areas keep clippings rotating and crush them. Robot lawn mowers don’t gather the clippings. They mash and leave them as instant lawn fertilizer. This is the reason why they are often used on a daily basis.
Their design prevents any objects from reaching their blades. They carry bump sensors (bumper contacts, switches, etc.) to detect objects in their path. Tilt sensors can block the blades or shut down the whole mower. Some even stops if touched by hand. Sonar systems can slow down the lawnmowers before any impact to reduce the damage.