Robotica Industrial Robots

In this document are related concepts, classification and robotic sensors types such as internal and external sensors, contact and non-contact sensors, and are described some it like as proximity, force, position, acceletarion. The point of this paper is strictly educative and the information on it; is a compile of books and informative documentation.

Introduction

The robotic has achieved great importance in a different scope of the, science, society, education, medicine, and industry among others. This kind of technologies was has been too how sources of inspiration for many movies in the cinematography industry.

The movies showing a robotic like as a humanoid machine that can do almost all the function of human behavior but this it is a futuring and ambitious vision of the that human want to achieve with developing of the robotics and the technologies that involve because currently exist several kind of robotics with shape and target different and the area where they are most used is the industry.

A robot can be defined as an automatic device that can do function ordinarily assigned to humans. The definition mention above can will be inferred that any machine that makes a function like a human such as a laundry machine, dish clean machine we can say that is a robot.

A definition more exactly about the definition of industrial robot is described by “Robot Institute American”, it says that an industrial robot is a multifunctional reprogrammable handle design to move materials, pieces or device specialization through of programmable movement for executing diversity task.

Exist different type of industrial robots like as cartesian robots (a), cilindic robots (b), polar robots (c), angular robots (d) and so on the following picture are some example.

[pic 1]

Among the different field that studies the robotic, they find the kinematic and dynamic of the arm, the planning and control of the moment of the handle, programming, intelligence of the robot but definitely the interaction between the reality and robot through the sensor robots is one of the most interesting topics in this area.

Sensor of the Robot Classification

The sensors of a robot can be classified into two big groups: internal and external sensor. The internal sensors refer to the information of itself robot such as position and orientation, velocity, force and acceleration. The external sensors getting information of the environment with the that interact the robot like as touch, proximity, and vision.

The internal sensors mostly of time are used for control and monitoring each part of the robot components whiles the external sensor permit having the control of the robot interaction whit the object.

Internal state sensors

Based on the information that the different sensor collects the control device decides of the control command corresponding to executing. To continuation are related some of the most used internal sensors and the parameters that are obtained.

 Position

• The encoder is a digital optical device that converts the movement into a sequence of digital pulses. Through the content of a single bit or the decoding of a set of bits, the pulses can be converted into relative or absolute measurements. In this way, the encoders are of an incremental or absolute type. In addition, each type can be linear and rotary in turn.

[pic 2]

Fig.1 Encoder

• The potentiometer is a variable resistance device that expresses linear or angular displacements in terms of voltage. It consists of a sliding pin that makes contact with a resistive element; As this contact point moves, the resistance between the sliding contact and the connections at the ends of the device changes in proportion to the displacement, x and θ for linear and angular potentiometers, respectively.

[pic 3]

Fig.2 Potenciometer

• The variable linear differential transformer (LVDT) is one of the most widely used displacement transducers, particularly when high precision is required. It generates an AC signal whose magnitude is related to the displacement of a mobile nucleus. The basic concept is that of a ferric core that moves in a magnetic field, where the field is produced in a way similar to the field of a standard transformer. There is a central core, surrounded by two identical secondary coils and the main coil.

[pic 4]

Fig. 3 LVDT

• Synchronizers and resolvers while encoders produce digital outputs, the synchronizers and resistors provide analog signals as output. These consist of a rotating shaft (arrow) (rotor) and a stationary housing (stator). Your signals have to be converted to the digital form by means of an analog to digital converter before the signal is input to the computer.

Velocity

Basically, all position sensors, when used with certain time limits, can give the speed, for example, the number of pulses provided by an incremental position encoder divided by the time consumed in doing so. However, this method imposes a computational load on the controller, which may be occupied by some other operations.

• Tachometer these sensors can directly find the speed at any time and without a lot of computational loads. These measure the rotation speed of an element. There are several types of tachometers in use, but a simple design is based on the Fleming rule, which states that "the voltage produced is proportional to the index of the inductive coupling". Here a conductor (basically a coil) is attached to the rotating element that rotates in a magnetic field (stator). As the shaft speed increases, the voltage produced at the coil terminals also increases.

[pic 5]

Fig. 4 Tachometer

Acceleration

Similar to the speed measurements that are given from the information of the position sensors, accelerations can be found at the rate of change with respect to the time of the speeds obtained by the speed sensors or calculated from the information of position. But this is not an efficient way to calculate acceleration since it will impose a heavy workload on the computer, which can reduce the speed of system operation. Another way to measure acceleration is by calculating the force that results from multiplying mass by acceleration.

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