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Mechatronics

Kiran — Fri, 05 Feb 2010 04:30:11 +0000

This article belongs to series “Mechanical Engineering Guide“. You can easily access other articles at QUICK LINKS page.

Mechatronics is very interesting subject and also very good option as career option. This subject is initialization to Robotics. In University of Pune, Mechanical Engineering students study this subject in last year or 4th year 1st semester. Syllabus of mechatronics is not needed to be explained. Here I will just make huge list and you will get the scope of the subject.

1. Introduction:

Mechatronics, measurement system, control system, concepts, response of system.

2. Flow and Pressure Measurement:

Rotameter, anemometer, McLeod gauges, pressure measuring devices.

3. Level And Strain Measurement, Length Measurements, Position Sensors:

Strain gauges, types of strain gauges, load cells, RTD (Resistance Temperature Detector), thermocouple, pyrometers, LVDT (Linear Variable Displacement Transducer), optical encoder, RVDT (Rotary Variable Displacement Transducer) etc.

4. System Models and Control System:

Mathematical model of system, electrical system, fluid and thermal system, rotational and translational system, electromechanical system, hydraulic system, open loop, closed loop system, feed back and feed forward control system.

5. System Response and Control Action:

Modeling of dynamic system, dynamic response to 1st order and 2nd order system, proportional, integral, derivative control actions, transmitters, controllers, switches and relays.

6. Analog Signal Processing, Digital Signal Processing and PLC (Programmable Logic Circuits).

That’s All or I should say, Is that all?

Thanks for Reading.

Sensors In Robotics

Kiran — Sun, 15 Nov 2009 06:14:04 +0000

Here we are talking about sensors used in the Robotics. As we know that robotics uses the sensors to its maximum limits, various types of sensors are used for various purposes in various application in various locations.

Classification of Sensors Used In Robotics Based On Physical Input Quantity:

Tactile sensor.
Proximity Sensors.
Range sensors.
Navigation sensors.
Vision sensors.
Miscellaneous sensors.

1. Tactile Sensors:

Tactile sensors are devices which indicate contact between themselves and some other solid object-in this case, an obstacle. This kind of sensors can be subdivided into two more sutypes:

Touch Sensors:

They are used to indicate that contact has been made between two objects without regard to the magnitude of the contraction force. A binary output signal indicates whether or not a contact has been made with the object.

Ex:- limit switches, micro switches etc.

Force Sensors:

They are also called as stress sensors. They not only indicate that the contact has been made but also the magnitude of the contact force between the two objects.

The capacity to measure forces permits the robot to perform a number of tasks. These include the capability to grasp parts of different sizes in material handling, machine loading and assembly work, applying the appropriate level of force for the given part. In assembly applications, force sensing could be used to determine if screws have become cross-headed or if parts are jammed.

2. Proximity Sensors:

Proximity sensors are devices that indicate when an object is close to other. How close the object must be in order to activate the sensor depends upon the particular device. The distances can be anywhere from few millimeters to several feet.

Proximity sensors can be used to detect the presence or absence of a work part or object. Another important application is sensing human beings in the robot work cell. Range sensors will determine the location of an object (work part) in relation to the robot.

Ex:- optical proximity sensors, acoustical sensors, magnetic field proximity sensors.

3. Range Sensors:

This is type of sensors which can be considered very near to proximity sensors. Range sensors measure the distance between the object and the sensor. These sensors are located on the wrist or end-effecter as these are the moving parts of the robot.

4. Navigation Sensors:

As name navigation indicates, this is kind of sensors which can be used for estimate positioning of objects. This kind of sensors can be classified in two main subclasses.

Relative Positioning Measurement:

They measure the signal within the robot itself. They can be again subdivided into:

Proprioaptive sensor.

Inertial navigation systems – Gyroscopes and Accelerometers.

Odeometry.

Absolute Positioning Measurement:

As name absolute, this sensors take measurements from some kind of fixed or universally fixed datum. Types Under This kind of sensors is:

Magnetic Compasses.

Global Positioning Systems (GPS).

Active Beacons – triangulation.

Landmark Navigation.

Model Matching – Map matching.

5. Vision Sensors:

Machine vision is concerned with sensing of machine vision and its interpretation by a computer. The typical vision system consists of the C.C.D. camera and digitizing hardware, a digital computer and software necessary to interface them. This interface hardware and software is after referred to as a preprocesser. The operation of the vision system consists of 3 functions :

a) Sensing and digitizing data.

b) Image processing and analysis

c) Application

For object recognition, along with processing, robot programming is also necessary.

6. Miscellaneous Sensors:

This category covers the remaining types of sensors and transducers that might be used for interlocks and other purpose.

This category includes devices with the capability to sense variables such as temperature, pressure, fluid flow, velocity and electrical properties. Hence this category includes sensors and transducers like tachometers. LVDT, Pr gauges etc.

Autonomous Mobile Robots Overview

Kiran — Tue, 13 Oct 2009 17:06:19 +0000

Introduction to Mobile Robots:

Robotics is very speedily growing and widely used branch of engineering. It have very large set of applications around, like in automobiles industry, electronics, computer industries, mechanical industries etc.

Now, we will move towards robots. Man is successful in creating the stationary robot and making its use for various applications. For example, robotic arm. Robotic arm is used in the automobile industries and electronics industries for automation purpose. These arms are very skilled in their work and perform the task in almost ideal time. Moreover, their operating cost is much less than the skilled human worker.

However, the main limitation of a robotic arm type stationary robots is that, it has to operate only in a defined area. Mobile robots are next to stationary robotic arms.

Mobile Robots/ Movable Robots:

As discussed before, mobile robot is movable, so it is necessary to have some locomotion system in it. Up till now, wheels and tracks are best options. Now a days, robots designers are looking towards newer ways of locomotion due to complexity in the operation of robot task. These ways includes, designing the robot having legs. Such robots have wider adaptation with working environment. Legged robots have necessary applications in the Defense and Aerospace Applications (Like NASA Projects). As stable robots start moving around in the uneven field, new problem arise which regard to the balancing of robot. This needs the installation of Leveling Mechanism in it.

Controlling The Mobile Robots:

No doubt, that to make robot work smarter and smarter designer have to install a wide types of sensors in it like distance sensors, level sensors, weight sensors etc. These sensors have the whole responsibility that the device will work as per design or not.

Mobile robots can be completely or partially controlled by the remote control devices. These devices communicates with robots through infrared or some similar medias. If area of working of robots is quite defined then direct wires could be used. But this limits the robot working area.

Again, robots can be autonomously controlled too. This is achieved by providing the program which pre-defines the robot task through program. Autonomous robots can act on their own, independent of any controller. The basic idea is to program the robot to respond to a certain way to outside stimuli.

General Applications of Mobile Robots:

Simple robots are used in homes and offices e.g. land moving robots whereas advanced autonomous robots like rover are used in space exploration. Micro robots are used for defense purposes and navigation. Mobile robots with stable legs will an important step in building stable humanoids.