More household robots mean fewer hours work for humans. An autonomous lawn mower robot could bring more satisfaction when you drink the coffee in the mornings.

With additional components and a little innovation was born the robot designed to cut the grass in small to large gardens or farmers. These smart machineries include mechanical parts, electronic systems and a lot of programming lines.

The household robotic industry is growing, and this is not a surprise in our days when we are using smartphones to control almost anything.

To cut the grass is not a simple task. The robot should be able to avoid collisions and obstacles, and at the same time it should take care to cut the grass at the desired height.

A fully autonomous robot is supposed to not require the human intervention in its activity. Even for actions like a detailed path to follow. This is the theory. In practice, it is really hard to build such a robot, but it is not impossible.

Before digging deeper into the features of a robot lawn mower, let us take a breath and understand the advantages and the disadvantages of this machinery.

Advantages

• such a robot is designed to replace at least one household chore;
• an autonomous lawn mover require a minimal intervention from the user;
• an autonomous lawn mover do not require guidance from the user;
• it is very easy to program a robotic lawn mower;

Disadvantages

• in some cases, an autonomous lawn mower, is not safety enough;
• recharging time for battery takes too much. Sometimes it takes hours;
• working time is very short, tens of minutes;

Without too many details, when the robot is used for the first time in a new location it must be able to work almost instantly. Here intervenes the system that controls the robot. It has a complicated architecture, too complicated to be described in a sentence. In this case, the most logical thing is to make a list.

The architecture of a system that control the robot lawn mower should:

• be able to explore the area;
• response in case of changes in the environment;
• monitor changes;
• identify objects;
• avoid objects;
• build the map of the area;
• wander;

In the development phase, a detailed simulation could help to develop the best system that control the robot. With or without simulation, a robot has to accomplish the three laws of robotics.

The design should include three main things: software, mechanics, electronics.

• the chassis;
• the drive motor;
• one or more blades;
• front and rear wheels;
• a mechanism that release the grass;
• control system – a mix of software and electrical systems;
• and a control panel;

In the following, I explore the functionalities and the main parts of an autonomous robotic lawn mower.

The control system

The word ‘autonomous’ means a lot in robotics. In this case, autonomous means that the robot think and take decisions based on information from the sensors.

Every robot brain runs a program with code lines in order to do what the user needs to do. In general, a robotic lawn mower is equipped with a simple control software where the owner can set the hours and days when the robot will start and finish the work.

Almost all robots released on the market are equipped to read clearly what the robot can do with displays.

The brain of the robot is a microprocessor able to control the sensors and actuators. The list of sensors is a large one and include sensors like GPS, tilt, accelerometer, infrared, etc.

How the robot navigate

An autonomous robot should include the ability to navigate without human intervention in a predetermined area. Back in time, in 2002 the University of Illinois and John Deere collaborate to design and built a self-driving tractor with ability to follow a predetermined path. Of course, the tractor was designed to work for agricultural tasks. The result was a robotic tractor that can follow the route with high accuracy.

A robotic lawn mower is designed with different navigation systems programmed to keep the robot in the desired area. These systems include GPS sensors to sensors able to detect the grass. In other words, all these systems should be able to keep the robot in the owner area and less in the garden of the neighbors.

The robot also should detect the working area. This detection includes a system that determines the position in space. This functionality helps the machinery to cut the grass optimized and in less time.

Back to the navigation system, a lawn mower robot can use the satellite connection, a video camera to detect a color line, a wire that surrounded the area or a grass detection sensor.

Using a satellite connection and navigation systems, the robot can determine its position and navigate in the specified area.

A simple web camera can detect a color line that represents the edge of the area when the grass has to be cut.

Most simple wires embedded in the environment can become the border for the robot in order to define the limits of the yard. The wire sends electronic signals to the robot in order to navigate in that area.

An intelligent navigation system uses a grass detector sensor instead wires to define the perimeter. The sensor can recognize the lawn and places where the grass is missing.

How to supply with power a robot lawn mower

Without power the robot is just a piece of metal, plastic, and electronics. The designers attach the robots different source of energy including solar power and batteries. Some of the robotic lawn mowers combine the solar power with batteries to increase the working time while other robots run only on batteries.

Most common power sources remain the batteries. The biggest disadvantages are that a set of batteries requires tens of minutes at a single recharge.

An autonomous robotic lawn mower should have the ability to return to the docking station when the battery is low and then back to work.

Safety

This is a special chapter in the designing phase. The designers should look very carefully at the safety system and take care that these works according to the specifications. Almost all the robotic lawn mowers have an emergency stop feature with the role to shut down the system at a press of a button. Other safety systems include a wireless emergency stop operable via an operated or Internet using a mobile device like a smartphone, tablet, or using a PC.

A safety system could also work to protect the robot. To ensure the protection of the robot, the engineers design systems that shut down the robot if a sensor detects rain, for example.

This article was last modified on 27 April 2015.