PowerPoint Presentation

Knight GearGroup 6Rene A. GajardoDo KimJorge L. MoralesSiddharth PadhiMotivationHeavy course work would require more materials.Posture is affected by the larger amount of things that a student carries. Knight Gear would allow for easier moving of school materials and more.Goals and ObjectivesEasy to use robot that follows the user using tracking algorithm.Carry a limited load of materials for the user.Onboard ultrasound sensors

SpecificationsComponentDesign SpecificationChassis1.5 in above ground Length = 19.5inWidth = 15.5inHeight (max) = 21.75inHeight (min) 12inUltrasound Detection3m Battery Life2 hoursBattery Charge Rate1.5 hours (electrically)Wireless Connectivity Range400 feet

Micro controllersOne central microcontroller All the heavy computing SensorsMotors, and accessories. Does not need to be very powerful, but enough to be able to handle and process all incoming data Data is simplified by the smaller, weaker, outer microcontrollers which handle the analog I/O from the devices. The group decided that a good choice would be to have one central microcontroller for all the heavy computing including sensors, motors, and accessories. The central microcontroller does not need to be very powerful, but enough to be able to handle and process all incoming data that is simplified by the smaller, weaker, outer microcontrollers which handle the analog I/O from the devices.

6Micro Controller Comparison MC68332Intel 8051PIC 18F452Atmega 2560Digital I/O15242454Analog I/O158816Operating Voltage5V3.3V5.5V3.3VCost$11.94$1.50$4.68$17.9811 pulse wave7Why ATMega 2560 ?Popular option amongst hobbyist with a large community for assistanceProgrammable in C using ArduinoEnough memory for our needsAllows Knight Gear to fully use all the Pulse Wave Modulation lines that it required for all of the ultrasound sensors and for the motor drivers. With a 3.3 volt operating voltage, 54 digital I/O pins, 15 of them being PWM, 16 analog inputs, and a large amount of documentation

This microcontroller allows for Knight Gear to fully use all the pulse wave modulation lines that it required for all of the ultrasound sensors and for the motor drivers. With a 3.3 volt operating voltage, 54 digital I/O pins, 15 of them being PWM, 16 analog inputs, and a large amount of documentation from different hobby websites make the Mega Pro a great low power option for the microcontroller for Knight Gear.

8Pin connections of Mega Pro 3.3

Ultrasonic Proximity SensorIt engenders high frequency sound waves (above 20,000 Hz), which is incorporated in these sensors, to measure the echo encountered by the detector, and is then received after reflecting back from the target.This is the basic concept of how Knight Gear will detect and follow its user.

Ultrasonic sensor plays an indispensable role in Knight Gear.

10ProductsResolutionReading RateMaximum RangeRequired VoltageRequired CurrentOperational TemperaturePriceXL-MaxSonar-EZ1cm10Hz300in-420in3.5V-5.5V3.4mA0C 65C $27.95XL-MaxSonar-AE1 cm10Hz300in-420in3.5V-5.5V3.4mA- 40C 70C$29.95LV-MaxSonar-EZ1 cm20Hz254in2.5V-5.5V2.0mA-$21.95HRLV MaxSonar-EZ1 mm10Hz195in 2.5V-5.5V3.1mA0C 65C$28.95Parallax PING))) 280151 cm10Hz118in5 V30mA0C 70C$29.99Why PING))) 28015 ?Precise, non-contact distance measurements. It is relatively easy to connect to microcontrollers PING))) 28015 measures distance from about 2 cm (0.8 inches) to 3 meters (3.3 yards). Robot side only receive signals, so cover the transmitterUser side only send signals, so cover the receiver

Sensors from MaxbotixParallax Ping SensorWireless CommunicationWireless communication is needed for localization of the user (which is the main feature of Knight Gear and its top priority). Some wireless communications looked at were:Wi-Fi Bluetooth, and ZigBeeZigBee turns out to be the final choice for wireless communication in Knight Gear. ZigbeeLow cost, low power, wireless mesh network. The following are the parameters of Zigbee

ParametersZigBeeRange10-100 metersOperating Frequency2.4 GHzComplexityLowPower ConsumptionLowZigbee contdZigbee comes in 2 series. The following is the comparison table between Series 1 and Series 2:

ParametersXBee Series 1XBee Series 2Range300 ft.400 ft.Power Consumption50mA @ 3.3v40mA @ 3.3vFrequency2.4 GHz2.4GHzData Rate250 kps250 kpsCost$22.95$20.95Based on the above table, Knight Gear was chosen to have a Series 2 XBee RF antenna. The main reason for this choice was to alleviate the budget for the group and availability of components. For Knight Gear, we will focus on serial communication using the XBee Series 2 antennas15PNP Inverter We needed to invert a serial signal from low to high using a PNP inverter. Using the serial out on the XBee and inverting it, we can get a high pulse trigger for the PING sensor

In order to trigger the PING ultrasound sensor with the XBee Series 2, we needed to invert a serial signal from low to high using an inverter. In order to make a low cost inverter, we decided to use a PNP inverter. Using the serial out on the XBee and inverting it as shown below in the figure, we can get a high pulse trigger for the PING sensor

16Solar PanelIncreasingly popularNo environmental pollution No need of burning fossil to generate the electricitySolar energy is no harm to our environmentGenerates electricity with no cost.

Solar energy is becoming increasingly popular as the people begin to take notice the high cost of electricity and the seriousness of environmental pollution. Advantages of solar energy are that they dont produce any environmental pollution and generate electricity with no cost. Since there is no need of burning fossil to generate the electricity, solar energy is no harm to our environment.

17Solar Panel contdThe material of the panel was important due to the different efficiencies of different materials in transforming solar energy into electricity. There are several different types of solar panel in used today. Some of the solar panels suitable for Knight Gear were the following: MonocrystallinePolycrystallineAmorphous

The material of the panel was important due to the different efficiencies of different materials in transforming solar energy into electricity. There are several different types of solar panel in used today. Some of the solar panels suitable for Knight Gear were the following:

18Solar Panel contdMonocrystallineMost efficient (13-17%)These are one of the oldest and most sturdy ones Expensive, require extra time and energyPolycrystallineEfficiency (11-15%)One generally needs a larger polycrystalline solar panel to match the power output of a monocrystalline solar panel.Less expensive than monocrystalline

Monocrystalline silicone solar panels are the most efficient type of materials to use for solar panels. These are one of the oldest and most sturdy ones. These panels are one of the most efficient by having an efficiency of 13-17 % However, since they are made with high silicon content they are more expensive than other materials. They also require extra time and energy to produce such photovoltaic cell.

These are also less expensive than their monocrystalline counter parts, but have a lower efficiency rate of 11-15%. As a result, one generally needs a larger polycrystalline solar panel to match the power output of a monocrystalline solar panel.

19Solar Panel contdAmorphousNon-crystalline siliconAmorphous solar panels are most found in calculators.The efficiency of amorphous photovoltaic cell is only about 6-8%.

This type of solar panel is non-crystalline silicon. Amorphous solar panels are most found in calculators. The production process requires only few raw materials therefore, the layer of semi-conductor coating is only 0.5-2 micro meters thick. The film of amorphous silicon is deposited as a gas on a smooth surface. Chemical process takes place to finish the process. The efficiency of amorphous photovoltaic cell is only about 6-8%.

20So, which one ? Polycrystalline solar panels To build our battery recharger for Knight GearEven though this is less efficient than monocrystalline panelsIt is very cost effective.we decided to use small monocrystalline solar panels to build our battery recharger for Knight Gear. Even though they are more expensive than polycrystalline panels, we feel that if we reduce the size we will minimize the amount of capital used to build this sub system.

21Wheels ConfigurationMechanisms to provide locomotion that is required for the Knight GearDifferential DriveAckerman DriveSynchronous Drive, andOmnidirectional DriveDifferential DriveWheels rotate at different speeds when turning around the cornersIt controls the speed of individual wheels to provide directionality in robotCorrection Factor may be needed to fix the excess number of rotations

This is the most common control mechanism for robot builders, especially for beginners. The concept is simple; Velocity difference between two motors drive the robot in any required path and direction. Hence the name Differential drive. Differential wheeled robot can have two independently driven wheels fixed on a common horizontal axis or three wheels where two independently driven wheels and a roller ball or a castor attached to maintain equilibrium.23ChassisCustom made chassis designed out of High Density Polyethylene (HDPE).Most chassis found where either too small or too big for our needs. Withstands heatWater-resistant

ParametersMeasurementsLength 19.5 inWidth15.5 inHeight (max)21.75 inHeight (min)12 in24Chassis contd

Control AlgorithmWe implement a PI controller instead of a PID controller to save memory.Runs only on current error and integral of previous errors.Using small constant multipliers to lower the deviation on Knight Gear.The error is determined by the time it takes for the signal in the users transmitter to reach both sensors on Knight Gear.Control Algorithm ContdThe microcontroller pings the radio frequency antenna on the user side transmitterThe user side transmitter then makes its Ping))) sensor emit an ultrasound waveThe ultrasound sensors on the robot pick up on the ultrasonic wave The sensors return how far away the user is according to eachThe data is then sent to the PI ControllerClass Diagram of Knight Gears Control Algorithm

Overall codeThe robot turns in the direction of the of the sensor which detected the signal first.The magnitude of the turn and the speed of the robot is calculated by the difference in time in which the sensors detect the user.

More flow charts 29MotorsGeared DC MotorsBigger, more powerful version of DC motor Used in robotics and other control situations where a small motor with lots of power is needed. The speed is generally controlled using pulse width modulation of the fixed input voltage. Can operate in both clockwise and counter clockwiseSpeed can be altered by varying the voltage applied to the motor.

Geared DC motor is a bigger, more powerful version of DC motor that gear reducer is integrated. The geared DC motors are very often used in robotics and other control situations where a small motor with lots of power is needed. The speed is generally controlled using pulse width modulation of the fixed input voltage. Like other DC motors, geared DC motor can operate in both clockwise and counter clockwise and its speed can be altered by varying the voltage applied to the motor. Input voltages range of the motor used for robotics range from 3-30V.

30Motors contSpur DC geared motors (x4)DC motor combined with a gearbox that work to decrease the motors speed but increase the torquePololus metal gear motor:

Operating voltage6VFree speed120 RPMCurrent80mA @ free runstall current2ATorque9.6 lb*cmCheck specs and have a column of measurements31Motor controllerMicrocontroller can decide the speed and direction of the motor, but provide very limited and small output current.

Motor controller provides enough current and voltage to the motor However, they cannot control how fast the motor should spin. Therefore motor controller and microcontroller need to work together to make the motors to move properly.

The motor controllers are designed to provide the enough current and voltage to the motor but they cannot decide how fast the motor should spin. Therefore motor controller and microcontroller need to work together to make the motors to move properly. Moreover, communication method between microcontroller and motor controller should be met. For Knight Gear, PWM will be used for the communication between the microcontroller and the motor controller. 32Motor ControllerH BridgeH bridge circuit is commonly used in robotics and other applications to allow the DC motors to run forward and backward

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10ModelL293DSN754410DRV8833BrandTexas Instrument/ StmicroelectricsTexas InstrumentTexas InstrumentOperating supply voltages4.5V ~ 36V4.5V ~ 36V2.7V ~ 10.8VTolerant peak output currents1.2A2A1AContinuous currents per each channel600mA1.1A500mAH-BridgesQuadruple-HalfQuadruple-HalfDualControl methodPWMPWMI2C / PWMInternal diodesYESYESYESPrice (from mouser electronic website)$1.12 $0.87 $2.58 Why SN754410 motor controller ?

Quadruple-Half h-bridge circuit -> control up to two motorsProvides sufficient continuous current of 1.1AProvides peak output current of 2A which is same as the stall current of the motors No extra diodes are needed that makes easy to implement the circuitCost effective

Texas Instrument model SN754410 will be used as motor controller for the Knight Gear. This model provides sufficient continuous current of 1.1A with lowest price thus this model seems very cost effective. Also, this model has standard pin packages for schematic design and no extra diodes are needed that makes easy to implement the circuit. It is designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications.

35Power source Rechargeable battery selectionNiCadNiMHAlkalineLi-ionVoltage1.251.251.503.6Capacity loadLowHighHighHighRecharge Cycle1000500 - 100010 - 50300 1000Charging Time1 - 1.5 hours2 -4 hours2 3 hours2 4 hoursDischarge Efficiency70 90 %66 %Varied by Capacity Load80 90 Operating Temperature-20 45 C-20 45 C-20 60 C0 45 CSelf Discharge Rate10%25% 5V LDO regulator (LM2940)MicrocontrollerMotor driver ICUltrasonic sensors5V -> 3.3V LDO regulator (LM3940)Xbee RF module (wireless antenna)Power systempower regulation cont.Block diagram of power system cont.Battery life test6V battery pack (robot side)

2100 mAH / 330 mA = 4.45 Hours

9.6V battery pack (robot side)

Free run -> 2200 mAH/320 mA = 4.81 hoursWith 10 lb -> 2200 mAH/1360 mA =1.13 hoursWith 20 lb -> 2200 mAh/3360 mA =0.46hoursPartCurrent drawsMicrocontroller105 mAMotor controller115 mAUltrasonic sensor (Rx)50 mAXbee RF module(Tx)55 mATotal330 mAPartCurrent draws4 x Gear motor @ free run80 mA *4= 320 mA4 x Gear motor with 10 lb payload340 mA *4= 1360 mA4 x Gear motor with20 lb payload1090 mA *4= 3360 mAXbee TestingThis figure shows how Xbee is programmed to give us the ID, high and the low for the signal which is shared by the sender and receiver.

Xbee Testing contd.This figure shows that the Xbee is communicating successfully.

PI Controller TestingThe values of the ultrasound sensors are printed in the comComponents of the PI controller are then printed Also the direction (left or right) of the turn is printedFinally the adjusted speed of the motors is printed

Technical Problems while building Knight GearInconsistency in devicesUltrasonic sensorsFaulty and burned out sensorsWeight sensorXbee Antennas

Questions?