Role of sensor in Precision Agriculture

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Slide 1:

Role of Sensors in Precision Agriculture Professor V. K. Tewari Machinery Systems, Ergonomics & Safety Department of Agricultural and Food Engineering Indian Institute of Technology, Kharagpur

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Precision Agriculture ? PA has been defined as an information and technology based agricultural management system to identify, analyse and manage site specific crop production to optimize profitability and sustainability of the production, as well as to protect the environment. -Robert et. al., 1995

PA Requires:

PA Requires System approach to reorganize the total system of agriculture towards Low input High efficiency Sustainable agriculture

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Modern Technology Use GPS GIS Computer software Automatic control Infield and remote sensing Mobile computing Advance information processing Tele communication

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Agricultural industry is now capable of gathering more comprehensive data on production variability in both space and time Hence for gathering of data we require means and sensors are one of these?

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Sensor: A device which detects or measures a physical property. Biosensor: A device which uses a living organism or biological molecules especially enzymes or antibodies to detect the presence of chemicals. Transducer: A device that converts variations in a physical quantity, such as pressure or temperature or brightness into an electrical signal or vice-versa 6

Sensors in Farm Machinery & Power:

Sensors in Farm Machinery & Power Wheel slip Speed Torque Fuel consumption Drawbar pull Noise & vibration EMG

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What is wheel slip? Slip is defined as relative movement in the direction of travel at the mutual contact surface of a traction device and the surface which supports it ( ASAE 1983 ).

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The efficient operation of 2WD tractors is prime concern of Indian farmers because of the rising operational cost. It has been reported that fuel cost alone accounts for 30-35% of the total operating cost. The optimization of tractor operational efficiency largely depends upon tractor operators who could adjust the operating parameters namely, speed and depth of operation.

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Point to point variation in cone index in field Variation in wheel slip Manual adjustment of depth control lever Operator senses the slip and moves the depth control lever only after a slip of about 30% had remains for 6 seconds ( Ismail et al . 1981) The average frequency of operation of hydraulic control lever is 3.13 times/min ( Arude et al., 1999 ) About 40% of the adjustments were to prevent the excessive wheel slip ( Dwyer and Rogie, 1972 )

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Three methods to measure actual speed 1. To measure the rotation of a non-powered wheel , Lyne and Meiring (1976), Clark and Gillespie (1979), Jurek and Newendorp (1983), Raheman and Jha (2007). Advantage- simplicity in construction, and ease of adaptability Disadvantage- Actual speed depending on soil conditions, weight transfer, skid of front tyre etc (error in slip not more than ±2%) Slip is not a directly measured value. It is calculated from two other measurements, that is actual speed and theoretical speed , which can be measured either directly or computed from the rotational speed and the rolling radius of the wheels.

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where V = Linear Velocity, m/s d = distance covered in one revolution of the wheel N = revolution per minute of the wheel 2. To measure the rotation of some form of an additional or fifth wheel device, Zoerb and Popoff (1967), Grevis-James et al. (1981), Erickson et al. (1982), Shropshire et al. (1983), Musonda et al. (1983). Advantage- Actual speed is independent of weight transfer, soil conditions and skidding of front wheel Disadvantage- Addition wheel, difficult in construction and addition

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3. To measure vehicle speed directly with a Doppler effect device, or using microwave radar, Stuchly et al. (1975), Wang and Domier (1989), Grisso et al. (1991), or ultrasonics, Micro-Trak (1987), Freeland et al. (1988) and Khalilian et al. (1989). Advantage - Accurate reading of actual speed Disadvantage - unproven reliability and does not record speed less than 1.8 m/s

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DEVELOPMENT OF SLIP SENSING DEVICE Encoder Design 1 5 4 3 3 2 6 1 2 1. Transparent disc 2. Optical slot sensor 3. Two ball bearings 4. Shaft 5. Water proof casing 6. Signal output cable The presence of clear and opaque stripes between the emitter and detector of the sensor is detected and converted into an electrical signal without contacting it.

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Working principle of slipmeter Microcontroller circuit development E f E r1 E r2 Calculation of rear and front wheel rpms Calculation of theoretical and actual speed Calculation of slip Input d f , d r , E f E r1 E r2 Display of N f, N r1 , N r2 Slip, V a Encoder for front wheel Microcontroller Signal conditioner Encoders for rear wheels

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Computation of slip in microcontroller Calculations of rear and front wheel rpm Calculation of actual and theoretical speed Calculation of wheel slip where E f = Number of pulses from front wheel in T seconds, E r1 = Number of pulses from right real wheel in T seconds, E r2 = Number of pulses from left rear wheel in T seconds, N f = RPS of front wheel, N r1 = RPS of right rear wheel, N r2 = RPS of left rear wheel, T = Refreshment time i.e 1.5 s, V a = Actual velocity, m/s, V t = Theoretical velocity, m/s, d f = Distance covered in one revolution by front wheel, m, d r = Distance covered in one revolution by rear wheel, m, and S = Wheel slip, %.

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Circuit diagram of the developed slipmeter

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Overall view of the developed slipmeter

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Installed encoders to the tractor Encoder#1 Encoder#2 Encoder#3

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Mounting on front wheel Mounting on rear wheel

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Implement move down DEVELOPMENT OF SLIP CONTROL SYSTEM Measured slip (S) Is S >UL Is S < LL No Stepper Motor Yes Yes No Implement move up Slip sensing device Working principle Stepper Motor Depth control lever Depth control lever

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Installation of stepper motor on the tractor

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Draft measurement system 2 1 1 4 3 5 1-Tensile and bending force sensor for lower link 2-Compression force sensor in top link 3-Angle of lower link horizontal plane 4-Angle of top link in vertical plane 5- Angle of lower link in vertical plane

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1 1 2 2 3 Three point linkage dynamometer. 4 5 6 4 5 6 Lower link tensile sensor, Lift rod bending sensor, (3) Compressive force sensor in top link (ring transducer), (4) Potentiometer in rocker shaft for depth , lift rod and lower link angle measurement, (5) Potentiometer for top link angle measurement, (6) potentiometer for lower link side angle measurement.

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Line diagram of fuel supply system using the flow meter.

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1 1 2 2 3 4 4 4 Flow meter2 Flow meter1 Flow meter1 inlet Flow meter2 inlet From the filter From the over flow line To fuel injection pump To the tank FI pump Injection over flow line 3 Over flow line Filter Fuel meters and fuel line arrangement. 2

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Fuel flow meter for return flow rate measurement Fuel flow meter for supply flow rate measurement 2 1 Position of two fuel meters. Experimental setup for fuel consumption measurement

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GEAR2 GEAR1 Fuel in Fuel out Magnetic poles Hall sensor 24 V DC Fuel flow meter Schematic diagram Fuel meter and Data logger connection. 100 ohm resistance

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Laptop Data logger Fuel meter Fuel pipe line 24 V dc Experimental set up for fuel consumption measurement. Calibration of fuel flow rate

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Pot1 1000 cc measuring cylinder Digital weighing balance Pot2 Fig. 8 Fuel flow rate measuring procedure for calibration. Pot2

Calculation of flow rate:

Calculation of flow rate Fuel in pot1 = M1 kg Duration = t min Fuel remaining in pot1= M2 kg Fuel return in pot2 = M3 kg So, Supply flow rate = (M1 – M2) × 60 / (t × density), l / h Return flow rate = M3 × 60 / (t × density), l / h Fuel consumption = ( Supply flow rate – Return flow rate), l / h.

Calibration curve of fuel meter:

Calibration curve of fuel meter (a) Flow meter1( supply) and (b) Flow meter2 (return) output at different supply flow rate. (a) (b)

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Different forces acting on the tractor 3-point linkage. Force Horizontal component Vertical component Bending (B) B H = B× sinɵ× cosɸ B V = B × cosɵ Tension (T) T H = T× cosɵ× cosɸ T V =T× sinɵ Compression (C) C H = C× cosɣ C V = C×sinɣ So, Draft, P x = T × cosɵ×cosɸ - B×sinɵ×cosɸ - C×cosɣ ɸ ɣ ɵ

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Line of pull in plowing operation Tractor-MB plow combination. Vertical soil reaction, P y = (T × sinɵ + B × cosɵ + C × sinɣ ) - W m

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Left lift rod Right lift rod Active Strain gauges Dummy gauges R1 R2 R3 R4 R5 R6 R7 R8 input R1 R3 R2 R4 dV R5 R6 R7 R8 Strain gauges mounted on lift rods and Wheatstone bridge circuit. Bending force measurement

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L3 H L2 L1 A O A ’ D E α Lt × sin α Lt × cos α B Taking moment about point O, B × L1 - Lt × sin α × L2=0, B = ( Lt × sin α × L2) / L1, L1=length of lower link=85.5 cm L2=OA ’ =43cm L3=A ’ D=lift rod length=56.5 cm DE= length of the lift arm Where, α = sin -1 ( H/L3) + lower link angle to horizontal plane( Ѳ ) H= vertical distance between A ’ and D Force analysis in lower link and lift rod. Calculation of bending force Ѳ Lt

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Strain gauges on lower links. Tensile force measurement

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Wheatstone Bridge Circuit Bridge for tensile force measurement.

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G1 G3 G2 G4 Proving ring G1,G3= active gauge on outer surface G2, G4= active gauge in inner surface Compressive force measuring transducer. Compressive force measurement

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Proving ring and strain gauge for compressive force measurement of top link. Compressive force measurement

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Design and Development of Tractor Axle Torque Measurement Sensor for 2WD Tractor

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THE MESUREMENT OF AXLE TORQUE Upadhyaya, et al. (1988) used dimensional analysis to evaluate the torque at axle shaft. T/rW = f (D/W, pbr/W, b/r, b/d, Cbr/W, s) They obtained this equation to describe axle torque: T/rW = a(1-be -cs ) Where, T = axle torque, r = rolling radius, W = dynamic load, and a, b, and c are the traction coefficients which are dimensional less and obtained statistically, by fitting experimental data to standard equation forms. Besselink, B.C. (2004) used torque load cells are used on an input shaft. They used hydraulic system in which the pressure drop across a motor is a function of torque and rotational speed. With a set of calibration curves, the torque can be determined from the measured pressure drop and the rotational speed. An extra benefit, in terms of analysis, is that the torque distribution between the drive wheels is able to be determined because the torque input is measured for each drive wheel.

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Reinoud, F. (1990) told that torque sensing has been performed by mainly using strain gauges connected to the axle with slip rings to enable the electrical contacting. They used non contact method for measurement of axle torque based on: (i) optical sensor, (ii) magnetic sensor, and (iii) capacitive sensor. Out of these sensors they preferred capacitive sensor. The capacitive torque sensor is basically a differential angular displacement sensor and is composed of two capacitive displacement sensors mounted on the axle and spaced a certain distance apart in order to enable the measurement of the twist angle. Capacitive torque sensor (a) Cross section and (b) longitudinal section (b) They used this relation between the twist angle t , over an axle length L in an axle of uniform diameter D and a modulus of rigidity G, at an applied torque T can be described by G steel = 8.10x10 10 N/m 2 for 10 mm thick steel and a sensing distance L = 100 mm in t/T = 10 -3 rad/Nm. Review contd… (a)

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Dong and Kyeong (1997) used slip ring based technique in which stain gauges have mounted on axle shaft as shown in figure. Billington, (1973) They have tested wheel torque are measured by strain gauge transducers and the outputs from the transducers are recorded on a 4 channel F.M. tape recorder. Culshaw, (1988) They have used these equations to measure rear axle torque: Where A = Coefficient of rolling resistance Cotr = Coefficient of traction rear Wsr = Weight static rear Wo = Weight overall H = Drawbar height L = Wheelbase F = Constant in equation for slip Pgr = Pull gross rear Review contd…

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Pandey et al. (2005) They found the relationship with different parameters with axle toque as: T = a 1 + a 2 W + a 3 P, T = a 1' + a 2' (δ/h) + a 3' P + a 4' P 2 W = Normal load P = Drawbar pull δ/h = Deflection/section height a 1 , a 2 , a 3 , a 1 ’ , a 2 ’ , a 3 ’ ,a 4 ’ are the regression coefficient Most commonly adopted method: by Zoz, F.M. and Grisso, R.D. (2003). Traction and Tractor Performance. ASABE Distinguished Lecture Series #27 Approximate agricultural tractor power relationships (drivetrain) Review contd…

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Understanding the type of torque to be measured, as well as the different types of torque sensors that are available, will have a profound impact on the accuracy of the resulting data, as well as the cost of the measurement. TYPE OF TORQUE AND ITS MEASUREMENT Static torque Dynamic torque TORQUE Reaction type In-line type Having no angular acceleration Having angular acceleration In-line torque measurements are made by inserting a torque sensor between torque carrying components. A reaction torque sensor takes advantage of Newton’s third law. e.g. how much torque is required to prevent the motor from turning. Measurement of torque

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Connection of the sensor from the rotating component to the stationary component Methods SLIP RING: Typical max speeds of slip ring will be in the 5,000 rpm range for a medium capacity torque sensor. Advantages: (i) Most common method (ii) Economical (iii) Perform well in a wide variety of applications (iv) straight forward, time proven solution Disadvantage: (i) At low to moderate speeds the electrical connection between the rings and brushes are relatively noise free, however at higher speeds noise will severely degrade their performance.

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ROTARY TRANSFORMER: In an effort to overcome some of the shortcomings of the slip ring, the rotary transformer system was devised. Advantage : By eliminating the brushes and rings of the slip ring, the issue of wear is gone. Disadvantages: (i) The system is also susceptible to noise and errors induced by the alignment of the transformer primary- to-secondary coils. (ii) Specialized signal conditioning is also required in order to produce a signal acceptable for most data acquisition systems. (iii) Cost is higher than slip ring. Rotary Transformer

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INFRARED (IR): This is also a contactless method of getting the torque signal from a rotating sensor. For high speed applications (even more than 2500 RPM) this is often the best solution for a rotating torque transmission. Advantage: Sensor’s output signal is digital, so it is much less susceptible to noise from such sources as electric motors and magnetic fields. Disadvantage: High cost FM TELEMETRY: These transmitters are used to remotely connect any sensor, whether force or torque. Advantages: (i) Much simpler and there are no other sensors, instruments, elaborate wiring, installation or safety concerns. (ii) Much easier to mount (iii) Very accurate and has significantly less error than slip ring strain gauge type sensors (iv) Requires much less maintenance. Disadvantage: High cost

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Install strain gauge on axle and turn it into the torque sensor FM telemetry Precise reading at all speed but costly Commercially available In-line torque transducer Precise reading at all speed but very costly Finally we can say that measurement of axle torque by conventional slip ring using strain gauge technique will be the economic solution as this can give relatively precise reading at low to moderate speed. Regardless of cost, contactless torque sensor will be the best solution among all. Possible solution for the development of torque transducer Precise reading, price is in acceptable range Install strain gauge on axle and turn it into the torque sensor Wireless transmitter Slip ring Precise reading at low to moderate reading and economic Install strain gauge on axle and turn it into the torque sensor

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Resistive strain gage sensors are chosen in this applications due to their higher accuracy, linearity, repeatability, etc. An effort should be made to develop a microcontroller based low cost wireless technology. (Radio Frequency) RF transmitter will be used for this application Block diagram of circuit of microcontroller based wireless transmitter Strain gauge torque sensor Signal conditioning & Power supply Microcontroller interface RF transmitter Antenna Receiver Microcontroller interface Data logger Laptop finally…

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Tyre DISC Flange Extended shaft Strain gauge Wireless transmitter Data logger Laptop/ CPU Measurement set up for torque sensor Wireless Receiver

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Flange coupling Extended shaft Strain gauge Disc Dynamometer Coupling Power transmission Motor Laboratory set up for validation of developed torque sensor

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Calibration MVC and RVE Selected muscles Flexi-carpi-radialis (FCR) Extensor digitorum (ED) Brachio-radialis (BR) Middle deltoid (MD) EMG measurement during rota-puddling operation

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0 15 30 45 60 0 5 10 15 20 25 30 Time, min EMG, V (10 -6 ) FCR ED BR MD 0 15 30 45 60 0 5 10 15 20 25 30 Time, min EMG, V (10 -6 ) FCR ED BR MD 0 10 20 30 0 5 10 15 20 25 30 Time, min EMG, V (10 -6 ) FCR ED BR MD Transportation Rota-puddling Rota-tilling EMG response during hand tractor operation

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Hand-arm vibration of hand tractor Handle adapter (Rasmussen, 1982) Mounting of handle adapter in hand tractor Biodynamic Basicentric Direction of measurement

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Vibration transmissibility in hand-arm system Location of measurement Accelerometer fixed in adapter Measurement of acceleration at wrist Measurement of acceleration at metacarpal

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Accelerometer Battery Data acquisition system Signal conditioner Personal computer Data analysis software Schematic diagram of the experimental set up for measuring vibration acceleration in the hand-arm system

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Vibration transmissibility in the hand-arm system of the operator Transportation Rota-tilling Rota-puddling

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Thank you…..

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