A humanoid robot is a robot with a body structure and features similar to that of a human. Three main primitives for a humanoid robot are sensors, planning, and control. These robots are generally having two types of sensors. The first one is proprioceptive sensors to sense the position and the second one is exteroceptive sensors to get data on what is being touched or senses ambiance.
These sensors are responsible to measure values of the internal system (like any machinery or robot); i.e. battery voltage level, motor speed, wheel load, robot arm joint angles, etc. Some of the proprioceptive sensors are described below:
Voltage and Current measurement:
We can measure voltage by using many techniques. Voltage is one of the easiest items in a robot to measure. Its measurement can help let you know the battery voltage or charging level. In the simplest way, an analog to digital converter (ADC) can be used to measure it.
For current in the circuit, there are two ways of measurement:
- The first way by using Hall Effect sensors: This sensor consists thin piece of a rectangular p-type semiconductor material such as gallium arsenide (GaAs) or indium antimonide (InSb) passing a continuous current through itself. When this sensor is placed inside a magnetic field, the magnetic flux lines exert a force on the semiconductor material which deflects the charge carriers, to either side of the semiconductor slab. This deflective motion of charge carriers such as holes or electrons is a result of the magnetic force they experience while passing through the semiconductor slab.
As these charge carriers move sidewards a potential difference is produced between the two sides of the semiconductor slab by the build-up of electrons or holes. Then the movement of the electrons through the semiconductor slab is affected by the presence of the external magnetic field. That effect is known as Hall Effect and these sensors use this principle for current detection.
- The second way is by using a shunt resistor: Here a low-value resistor (few milliohm) use. Bypassing through it you can measure the voltage drop and using ohms law determine the current in the path.
This kind of sensor tells the robot if it is tilted and the angle of the tilt. It is also known as a tilt sensor. Basically, it measures the angle of tilt of objects based on gravity in various applications.
These sensors are like a digital compass. A magnetometer measures the magnetic field for all three physical axes (x, y, and z) in microtesla. It measures magnetic induction or magnetic field intensity. Often a magnetometer is integrated with inclinometers and they are sold as 3D inclinometers.
This kind of sensor acquires information from the robot’s external environment; i.e. measuring distance, light intensity, sound pitch, and amplitude, etc. So we can say that exteroceptive sensor measurements are interpreted by the robot in order to extract meaningful environmental features or senses. Sensors such as CAMERA, LIDAR, RADAR, Thermal infrared scanner, Touch screens, and much more come under this category.