Tuesday, May 22, 2012

Force Sensors

Measuring force becomes very important in some cases like surgical instruments, robotic arms, laproscopic devices, etc; where the force applied is very minute.

In such cases, the force can be measured by using various sensors like;
  • Strain Gauge
  • FlexiForce Sensors
  • Piezo Disc
Strain Gauge

It is the most common device for measuring force. It is named so because, it is used to measure force through the strain produced in it. It consists of an insulating flexible backing which supports a metallic foil pattern as shown in the figure. 

This gauge can be fixed (mounted) onto the object, whose strain/force is to be calculated, through a suitable adhesive like silicone or cyanoacrylate. When the object is deformed due to any applied force, the strain gauge experiences tension/compression based on the nature of the force, which causes the resistance to change. This resistance change can be measured by connecting this to a Wheatstone bridge network.
    
GF=\frac{\Delta R/R_G}{\epsilon}
where
\Delta R is the change in resistance caused by strain,
R_G is the resistance of the undeformed gauge,
\epsilon is strain and
GF is the gauge facto.
For metallic foil gauges, the gauge factor is usually a little over 2. For a single active gauge and three dummy resistors, the output v from the bridge is:
v=\frac{BV \cdot GF \cdot \epsilon}4
where
BV is the bridge excitation voltage.
 FlexiForce Sensors
A FlexiForce Sensor is another kind of sensor that is used to measure force. It is shown in the figure. It is an ultra-thin, flexible printed circuit. It is constructed of two layers of substrate (polyester) film. 

On each layer, a conductive material (silver) is applied, followed by a layer of pressure-sensitive ink.

 
Adhesive is then used to laminate the two layers of substrate together to form the force sensor.

The active sensing area is defined by the silver circle on top of the pressure-sensitive ink. Silver extends from the sensing area to the connectors at the other end of the sensor, forming the conductive leads.
     
This can be mounted on the object on which the force is to be measured. When the force sensor is unloaded, its resistance is very high. When a force is applied to the sensor, this resistance decreases. The resistance can be read by connecting a multimeter to the outer two pins, then applying a force to the sensing area.

Advantages of FlexiForce Sensors over Strain Gauges
  • Direct force measurement - measures load directly as opposed to correlating strain of an assembly with load.
  • Larger dynamic range (resistance range from MΩ to KΩ).
  • Simpler Electronics - simply measured with multimeter or integrated with inexpensive circuitry.
  • Lower cost - standard sensors start at $65 for a 4-pack.
  • Easier to integrate - simple mounting process.

 Piezo Disc
A piezoelectric sensor is a device that uses the piezoelectric effect to measure pressure, acceleration, strain or force by converting them to an electrical charge.

A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated).

Metal disks with piezo material, used in buzzers or as contact microphones


References

http://en.wikipedia.org/wiki/Strain_gauge
http://www.tekscan.com/flexible-force-sensors
http://en.wikipedia.org/wiki/Piezoelectric_sensor

Thursday, November 10, 2011

The HOT SPOT Technology

The Saga of LBW and Caught Behind
        In the early eighties, they introduced Stump Cameras to detect LBW and caught behinds, which served as a helper for the umpires to provide accurate decision. But, as years went on,the technology grew along with cricket and saw the invention of Snickometers in nineties. Still, the people of Channel 9, one of the great broadcasters of cricket in the world, were not satisfied. So, they invented The Hawk-Eye Technology in 2002.
      
       Still the big technocrat giants didnt sleep. They wanted to make another technology which will be still more accurate in judging these factors. So, they invented The HOT SPOT Technology during the 2006 Ashes Series.

What is hot spot?
       It is an infra-red imaging system, which employs infra-red cameras to capture the happenings of the ground. The basic principle of physics is applied here, which states that, infra-red rays are emitted by hot bodies. Hence, when two bodies come into contact, the impact produces some heat, which emits infra-red rays. Special infra red cameras are used to capture these images.

          Two or more infra-red cameras are situated in suitable parts of the ground on both the sides. They constantly record the proceedings of the ground. They are brought into effect, when there is a suspicion on whether the ball hit the bat or pad in the case of a Leg Before Wicket (lbw) appeal; and also to detect the edge in the case of a Caught Behind appeal.
       

            The infra red camera shows a series of color spectrum, which depicts the range of heat distribution in the focused area. When, the ball makes an impact on either the bat or pad, the heat generated is shown by a white spot on the impact area. From this, we can conclude the result. This technology is more accurate and produces the best result than the previous techniques. The above pictures shows two typical infra red images recorded by the IR camera. THe impact produced by the ball on the bat and pad can be seen by the white spot.

           The following video shows how hot spot proved to be correct at a place where Snickometer judged wrongly in a test match between Sri Lanka & England. The Snicko suggested an edge, where as the Hot Spot proved its predecessor wrong.
video

Why India Cannot Use it
            One of the major drawback in Hot Spot technology is that it cannot be used in the Subcontinent countries and South Africa. This is because, the average temperature of these places is usually 30 deg Celsius, which is very high for an IR camera to capture it as the whole capture area will be white, hence, any faint edges cant be determined by this technique.
            
              Apart from this, the Hot Spot proved to be a very healthy and useful innovation in the field of cricket. But, there is no end to innovations, as in future we might see even better techniques or even better improvisations of this technique can be done so that it can also be used in hotter countries.

Thursday, November 03, 2011

THANK YOU MECHATRONICS!

         MECHATRONICS!!! The buzz word that spread around the class for these four years... MCT 2008-12 batch is well known for its unity amidst the diversity in the people. The variety ranging from Pudukkottai to Noida... but the unity prevails with no barriers in language.
         Just as all mentioned in their most emotional speech today, that these four years crossed us like a whisker, is really true. This college life is very short-lived but will remain the best in our life. Here are some of the glorious moments of the FAREWELL which took place on 2/11/2011 at 1:30pm in VKJ217 of Vishwakarma Joth (School of Mechanical Engineering), SASTRA UNIVERSITY.


         The whole party started with voting session starting at 9am in the morning. Organized by Shweta Thiyagaran, Shravya Sri, Sriram, Aadhithya, Agastheesh, Gautham and Dhivyasimhon had some of the most unanswerable questions. The votes was counted and the FAREWELL commenced after the completion of attendance AKD sir's attendance for Industrial Robotics, at 1:30pm.

            The results of the Various categories of polls are;

PADIPS :
                 Winner - Sravan
                 Runner - Arun
LATE-LATIF :
                 Winner - Dhivyasimhon
                 Runner - Ravi Kumar
SLEEPY-HEAD :
                 Winner - Nambirajan
                 Runner - Agastheesh
OVER BANDHA :
                 Winner - Nirmal Kumar
                 Runner - Narasimhan
STYLE ICON :
                 Winner - Ashwin. B
                 Runner - Shanmugham
MASS :
                 Winner - Aadhithya
                 Runner - Siva Karunakaran
JALDRA :
                 Winner - Nambirajan
                 Runner - Prasanna
QUESTION BANK:
                 Winner - Nirmal Kumar
                 Runner - Upendran & Chittaranjan
KADALAI :
                 Winner - Shanmugham
                 Runner - Harish
SMILE :
                 Winner - Ashwin. B
                 Runner - Swetha
DRESSING :
                 Winner - Ashwin. B
                 Runner - Aswin. V
MOBILE MANIAC:
                 Winner - Sri Krithiga
                 Runner - Venkataraman
BUNK STAR :
                 Winner - Narasimhan
                 Runner - Aadhithya
JOVIAL PERSON :
                 Winner - Hari Prasanth
                 Runner - Dhivyasimhan
PERFECT : 
                Winner - Nachiketh Pal
                 Runner - Riazul Ashraf
LOUDSPEAKER :
                 Winner - Chittaranjan
                 Runner - Nirmal
TOTAL DISASTER : 
                 Winner - Chittaranjan
                 Runner - Vinodh
TENSION PARTY :
                 Winner - Srinath Redd
                 Runner - Balamurali & Vinodh
BEST BUDDIES:
                Winner - Swetha-Sravya
                Runner - Prasanna-Arun Babu
SILENT:
                Winner - Arun
                Runner - Sudharsan


MR. MCT
NAMBIRAJAN

MISS. MCT
SWETHA THIYAGARAJAN


SPECIAL AWARDS:
BEST BIKER - Nambirajan
BEST GYM BODY - Karthick
BEST NICK NAME -  Botha (Siva Karunakaran)
KALAI MA-MANI AWARD FOR DANCE - Anand. S


              The award show was followed by some mimic performance by our Aadhithya, Kaushik & Dhivyasimhon on the various personalities that we had come across in our four semesters. It was an exciting fun filled segment which brought the audience on their feet and there was full of claps all around. One of the major part is, Aadhi's mimic as Simbu, TR and Vijay.

                   Then suddenly to everybody's astonishment, Aadhi came to the dais and gave a heart touching speech. It was a fully emotion filled moment. Following Aadhi, many gave some emotional speech and expressed their feeling about being with "The 62". Nachiketh reminded of one funny incident about Chittharanjan's Wolverine style beard in Fluid Mechanics class. Chittharanjan challenged us to come to SASTRA on the same date, 4 years later; on 2/11/2015, for a MECHATRONICS REUNION MEET. Whereas, Krishna Teja, the ever-different man, said that he never miss us, as he have us in his heart forever.

                    Prem Sir, was then called upon as the chief guest to this party. He came with a news that he got his promotion (although it was an unofficial news), the whole class broke in to congratulate our sir. He was then asked to address the class, but he was too shy to express his views. Then finally he wished us good luck and left. 
    
                   Finally, coke and kurkure packets were within the class to mark the end of the FAREWELL, which was followed by hugs and wishes all over the class within "The 62".

                     An unforgettable day in MECHATRONICS BATCH 2008-12 history... A moment to be cherished and remembered by all... 

THANK YOU MECHATRONICS!
FOR BRINGING US TOGETHER!!

Saturday, October 22, 2011

Megafactories: Rolls Royce: Videos

Rolls Royce (RR), another world's luxurious car manufacturing company, uses human labour for work to bring precisions and a perfect finish to its sophisticated handcrafted cars!
Look at the following videos.


Thursday, October 20, 2011

Evergreen Lamborghini Plant: Videos


Can u believe if i say that, the world's one of the best luxurious and fastest car manufacturer, Lamborghini, uses a mostly manual manufacturing plant!
Yes, the Lamborghini manufacturing plant prefers to use manual labor to manufacture one of the fastest car in the world. Except a few parts, most of the plant is fully manually operated and manually assembled. They use highly skilled and  specialized labor to do their process.. 
Take a look at the following video to see the  manufacturing of one of the world's fastest car!!



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