1. Proceedings of 2011 The 3rd International Conference on Machine Vision
Design and Development of LED Based Irregular Leather Area
Measuring Machine
Jamal.A.Khan 1
1
College of Engineering, National University of science and Technology, Karachi, Pakistan.
Karachi, Pakistan.
Abstract. Using optical sensor array, a precision motion control system in a conveyer follows the irregular
shaped leather sheet to measure its surface area. In operation, irregular shaped leather sheet passes on
conveyer belt and optical sensor array detects the leather sheet edge. In this way outside curvature of the
leather sheet is detected and is then feed to the controller to measure its approximate area. Such system can
measure irregular shapes, by neglecting rounded corners, ellipses etc.
To minimize the error in calculating surface area of irregular curve to the above mentioned system, the
motion control system only requires the footprint of the optical sensor to be small and the distance between
the sensors is to be minimized.
In the proposed technique surface area measurement of irregular shaped leather sheet is done by defining
velocity and detecting position of the move. The motion controller takes the information and creates the
necessary edge profile on point-to-point bases. As a result irregular shape of leather sheet is mapped and is
then feed to the controller to calculate surface area.
Keywords: leather sheet, Pinwheel, Irregular shape, Measuring Systems, surface area, Planimeters,
Optical Sensor, image processing
1. Introduction
Earlier industrial solutions to the surface area measuring problem were based on manual or less accurate
techniques. Now days due high production and quality demands systems need to be automated and sensed
data to be storage for calculating the tolerance to get the accuracy, for this electronic machinery is the only
competent solution. Human placement on leather measurement machinery can cause serious health problems
and it adds to the labor cost. Moreover, the calculations done manually depend on the experience of the
operator and the quality of the solution is not even consistent for a single given instance of the problem as it
also vary from time to time.
The proposed system aims to develop an automated signalling system and provide accuracy. The
proposed system has the following features.
 It is quick, while having negligible errors in calculation.
 It approximates the curves as polygons.
This problem type is defined as a problem category where a two-dimensional irregular shaped item has
to be completely accommodated by a two-dimensional polygon object. This paper mainly addresses the two-
dimensional area measuring of irregular shape problem [9].
2. RELEATED STUDY
2.1. Pinwheel Mechanism:
The international standard for Turner machine is Pinwheel mechanism [1]. In which a driven feed
roller coupled with rows of friction driven wheels having pins in their rim. Leather presses the pins in the

2. pinwheel up down to show the presence or absence of the leather at the desired position thus creating the
map of the leather on a paper sheet or on a dial. The area of leather is then calculated from the pin press
record as showed in Fig. 1 [2].
Fig. 1: Pinwheel Mechanism: International standard for measuring leather sheet.
2.2. Roller Planimeter:
Roller Planimeters are commonly used for computing the area of leather sheet in the leather industry.
Roller planimeters are attached to wheels that allow unlimited horizontal travel and vertical travel within the
limits of the arm movement. Unlike Pinwheel Mechanism it is not "pinned" down to work area. Roller
planimeters can roll all over the place without the restriction of an attached base. [3]
The Popular Mechanical planimeters are more economical for leather measurement. These systems are
usually of maximum counting capacity of 4 digits (9999). Electronic Planimeters are more accurate and are
based on memory and signaling system and they offer more speed and calculate scale factor automatically
[3] [10]. In case of Mechanical planimeter scale factor need to be calculated manually. The scale factor is the
multiple of x and y scale parameters. Its accuracy is 0.2% of the measured area[7].
2.3. Vision Based Leather Area Measuring Systems
Vision Based leather area measuring systems take images between different points marked on the leather
sheet and then extract the area of interest which in the case is leather of out the complete image and at last
area is measured through pixels to area conversion software's such as Bersoft image measurement software.
Both specialized hardware and Software's are used in these systems. [4]
3. ANALYSIS
Pinwheel, Roller Planimeters and Vision Based leather area measuring machines are all internationally
used machines for measuring surface area of leather. Each of the discussed methods lack to fulfill recent
industrial requirements such as Pinwheel mechanism is international standard but is very slow and is not
based on signaling system [1]. Secondly Roller Planimeters are based on memory and signaling system but
they slow [3]. The last discussed system are based on Vision which are very expensive, slow and need
calibration of individual parts such as camera, variable speed linear rail actuator and others [4] [8].
In short none off the presently available system fulfills every current industrial requirement which require
a system to be fast, accurate and self calibrated which results as production increase.
4. PROPOSED TECHNIQUE
Leather sheet is passed through IR transceivers; triggering of which are dependent on presence or absence
of the sheet. This is then to be feed to the microcontroller which accumulates the pattern of the sheet. The
pattern is then displayed on the LCD in terms of number of pieces passed through the IR transceivers.
4.1. Functionality:
The This process will start at the first pulse from any fist sampled piece of width represented by Y
which will be high if any IR transceivers connected in „OR logic‟ represented by X1, X2, X3…X7 will be
high and will continue until any of Yn drops to low. As shown in figure Yn represents sampled Length piece
under observation, whereas X1 - X7 represents width of the section under observation detected by IR
transceivers. Triggering of IR transceiver shows the presence or absence of the leather sheet at the desired
location [5]. The system "hold and accumulate" feature measure the area of each segment starting from the
first sensor to be triggered to the last segment and in last it add up all the segment to calculated the total area.

3. Fig. 2: Leather sheet placed on sensor array.
LED will display the presence or absence of sheet for each length patch. When whole piece is passed,
LCD will display the total area of leather piece in Sq inches using mathematical formula stored in
microcontroller. Sampled time is the time after which controller acquires the data from the microcontroller is
to be feed into microcontroller. For monitoring purpose complete Pattern of leather sheet is then transferred
to CPU using MAX 232 serial interface.[6]
4.2. Block Diagram:
Fig. 3: Block Diagram of the Process.
4.3. Processes Flow:
Fig. 4: Processes Flow.
4.4. Variables:
X = Width of the section under observation in mm
Y = Length of the section under observation mm
Z = Area of the section under observation mm2
Ts = Sampling time in seconds
S = Conveyer belt speed mm/sec
Ns = Number of active sensors
As = Sensor footprint in mm
4.5. Calculations:
Revolution Linear Actual
S. No. Frequency
(HZ)
RPM Motion Value
revolution/s (Inches/Sec) (Inches/Sec)
1 10 120 160 120
2 20 240 320 240
3 30 360 500 360
4 40 480 640 480
5 50 600 800 600
Table 1: Frequency of Motor to its equivalent Linear Motion.
160 (inches / second) = 4.06400 m / s
S = 40.64 mm/sec
If the sampling rate is a sample after every second.
Yn= S * Ts
Xn = N * As

4. Total Area = Z = = + + +….
Footprint of Sensor:-
5mm
4mm
For Z6: -
X6 = No. of triggered sensors * As = 4 * 4 mm = 16mm
Y6 = S * Ts = 40.64 mm/sec * 1sec = 40.64 mm
Z6 = 16mm * 40.64 mm = 650.24 mm2
Total Area = Z = Z1 + Z2 + ……+Z29
5. CONCLUSION:
Technique % Error Signaling System Calibration Cost
Pinwheel 2 N/A External Low
Roller Planimeter 0.2 YES External High
Vision Based 3 YES External High
Photo-electric 0.04 YES Self Low
Table 2 : Conclusion.
6. RESULT:
The proposed system is very fast as it uses transportation mechanism to measure the area. Secondly, due to
the involvement of only a few moving part the system has less vibration. The accuracy of the system depends
upon the footprint and the distance between the sensors. As the calculations are bit simpler so a less
expensive controller can easily fulfill the task. The error in system can easily be found using any regular
object of known area such as paper or plastic.
7. ACKNOWLEDGMENT:
This is to acknowledge the indispensible support and contribution of Air Cdre. (R) Engr. M. Khalid
Hussain, Dr. Syed Irfan Hyder, Mr. Iqbal Khan, and Mr. Taifoor Safdar in this academic article. Without the
advice, recommendations and motivation of these gentlemen, this paper would not have been possible.
8. REFERENCES:
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Tanners APRIL 1998.
[3] Engineer Supply "http://www.engineersupply.com/ About-Planimeters.aspx", Jan 2006
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[7] Penna, M.A. "Camera calibration: a quick and easy way to determine the scale factor" Pattern Analysis and Machine
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[8] “Specialty Motions, Inc,” http://www.smi4motion.com/ smi2/solutions / linear-actuatorpackages/variable-speed-
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