Operators Manual Assistive Robotic Device. Michael Khalil and Alon Dagan Team 5

Transcription

1 Operators Manual Assistive Robotic Device Michael Khalil and Alon Dagan Team 5

2 Important Safety Instructions General Guidelines The robotic arm is meant for assisting children with cerebral palsy. It is not a toy! Assistive robotic arm is not intended for gripping or interacting with humans or other living creatures Be aware that gripper may drop items. Do not use gripper with fragile or delicate objects. Assistive robotic arm is not intended for use over periods greater than one hour. Overheating may occur. The device should not be operated while under the influence of alcohol or illicit drugs. Electrical Hazards The assistive robotic device is not meant to be wet or submerged in any liquids. Do not attempt to power with alternating current. Do not pull or tamper with any of the wiring. Do not operate if wires appear frayed or broken. Mechanical Hazards Keep hands and body parts away from the mechanical arm while in operation to avoid pinching. Base unit is heavy. Dropping unit may cause damage to robotic arm as well as personal property. Never operate robotic arm without enclosures fully on. 1

3 Parts and Accessories Pictures of parts and accessories will be included when fully assembled. Controller Box Arm Enclosure Electronics Enclosure 2

4 Features Joystick Control Control box contains two digital joysticks used for arm control. One the joystick labeled Gripper/Height controls the opening and closing of the gripper as well as the height of the unit. The other joystick controls either the motion of the shoulder and elbow joints or the wrist mechanism depending on the mode toggle switches. Toggle Switches The toggle switch labeled Wrist mode/ Arm mode changes the joystick control from operating the wrist to operating the large motions of the arm. The other toggle switch changes between X Y coordinated control and joint control. These toggles do not affect the Gripper/Height joystick. 3

5 Table of Contents 1 Introduction 1.1 General Overview Step by step instructions on usage Maintenance 2.1 Electrical Mechanical Environmental 27 3 Technical Descriptions 30 4 Trouble Shooting 53 5 References 69 4

6 1 Introduction 1.1 General Overview The assistive robotic arm is composed of a gripper, a wrist mechanism, an elbow, a linear actuator, a rotating shoulder mechanism, a base clamp and an electronics box. Connected to this arm via a ribbon cable is the control box. This should always remain connected together and care should be taken not to stress the wire Gripper The gripper mechanism consists of a vise-like grabbing component connected directly to a servo motor. These components work together to allow for a sturdy grip that will not endanger the client or his peers. Figure : Gripper for the Assistive Robotic Arm Wrist The wrist mechanism will act to rotate the grabber based on commands from the client. This motion is important for manipulating objects and grasping horizontal objects. The wrist will pan and tilt 90 degrees and will be controlled by the joystick. In order to accomplish this, a camera adjustment pan tilt system will be used. This consists of two servo motors in a special encasement. It consists of ball bearings that will enable smoother and sturdier motion of the gripper mechanism. 5

7 Figure : Wrist mechanism Elbow Joint The elbow mechanism utilized in this design will operate in a single x-y plane specified by the elevator mechanism. The elbow joint will be controlled the microprocessor by means of pulse width modulation in conjunction with the servo motors. It is important that the elbow be able to support its own weight and the weight of a load without sagging or breaking. This joint will consist of a servo motor attached to a servo horn. The servo motor will rotate the forearm and gripper while the upper arm is sturdily fixed to the elevator mechanism. In this way the joint will be able to move reliably in one plane. The servo is placed in a power gear box so that it is more resistant to side loading which could easily damage a servo horn as opposed to the gear which is a much sturdier alternative. 6

8 Figure : Servo elbow attachment. Figure : Elbow servo Linear Actuator The linear actuator acts to lift and lower the XY plane of motion of the robotic arm. This is ideal for lifting objects straight up to reduce chance of tipping or spillage. The linear actuator we are using has a six inch stroke which allows for a change in height of up to 6 inches without moving the wrist mechanism. The linear actuator can be seen below in its extended configuration. 7

9 Fig : Linear actuator in extended configuration. The linear actuator is mounted to the arm with a custom machined bracket that limits the free rotation of the arm. This bracket can be seen in the figure below. Fig : Linear actuator mounting brackets Shoulder Joint The shoulder servo is mounted below the linear actuator and supports the entire robotic arm. It is important that this servo be able to support and move the entire load of the arm. To accomplish this task a Hitec HSR-599TG servo is utilized in conjunction with ServoPower Gearbox. Affixed to this gearbox is a ServoPower round servo horn 8

10 which acts as a rotating platter for the shoulder subunit. The HSR-599TG servo can be seen below alone as well as in its gearbox. Fig HSR-599TG Servo. Fig Controller The controller integrates two joysticks and two toggle switches. Between these mechanisms the entire arm can be controlled. Digital joysticks are used as this will allow for steady motion regardless of how far the joysticks are pressed. The controller is connected to the main electronics box with a ribbon cable. The power switch is on the main electronics box. 9

11 Fig : Controller design Electronics The control of the robotic arm is almost completely accomplished through microprocessor control. This is accomplished by a PIC16F877. The microcontroller was programmed with a novel program allowing for the output of five variable pulse width modulation signals. These signals are sent to the servo motors to actuate the arm. The schematic for the printed circuit board can be seen below. Fig : Electronics schematic. 10

12 1.2 Usage Instructions 1) Attaching the Robot Arm to the Table The Base of the Assistive Robotic Arm is also the attachment point for the arm onto the table or wheelchair. The base is a clamp with two knobs to tighten onto any almost any surface. It is a universal joint that can be used on almost any firm table or the arm of a wheel chair assuming that it is extremely sturdy. The clamp is made out of steel unlike the rest of the device because it needed to be heavy to stand and keep the robot arm from collapsing. It is essential to make sure the arm is securely fastened onto the mounting surface so that it does not tilt or fall off. It is fairly heavy and is a serious risk if it falls off the arm and on somebody s foot. If securely fastened this should not be a problem at all. 2) Hooking the Assistive Robotic Arm to Power To start operating the assistive robotic arm start by verifying that it is hooked to the 12 V battery and this current prototype requires another 5V power source because of issues with the arm requiring too much current. This could be fixed in the future by giving 12V to a powerful 5V voltage regulator in the PCB before the power hooking up to the holes labeled 5V in the PCB. The reason 12V is used is because the linear actuator in the elevator mechanism operates at maximum speed and efficiency at this voltage. Do not exceed 12V because it may damage the linear actuator. The linear actuator can however run at voltages less than 12V however it will operate at a much slower speed and will not be as practical as if it was operated at the recommended 12 volts. It is also recommended that Deep Cycle Batteries be used instead of an ordinary car batter because it is capable of providing a lot of current which is required by the motors unlike the car batter which only gives current upon starting the engine. 3) Click the Power Switch The next step is to flick the power switch that will be located in a box. This switch gives power to the microcontroller inside the Black Box which contains the PCB. 11

13 4) How to Control the Shoulder Mechanism (Single Joint Control) The Arm should now be fully powered and ready to operate. The Control Box should contain the 2 digital Joysticks and 2 Toggle Switches. The shoulder mechanism is controlled by moving the first digital joystick from right to left. - Make sure that the Toggle switch that controls the X/Y mechanism is not depressed. - Make sure the Toggle switch that controls the Wrist Mechanism is not depressed Figure Digital Joystick 1 This rotates the base of the assistive robotic arm which consists of a servo encased in a powerful gear box with a 10 round servo horn. It rotates the entire robot arm similar to the human motion. 5) How to Control the Elbow Mechanism (Single Joint Control) After the battery is hooked up and the power switch is depressed the Elbow Mechanism should be ready to operate. The elbow mechanism is controlled by moving the first digital joystick from up and down. 12

14 - Make sure that the Toggle switch that controls the X/Y mechanism is not depressed. - Make sure the Toggle switch that controls the Wrist Mechanism is not depressed. The elbow mechanism is operated using a servo in a powerful gearbox with a unique aluminum servo horn that was fabricated to attach the wrist mechanism of the assistive robotic arm to the elbow mechanism. 6) How to Control the Shoulder Mechanism & the Elbow Mechanism (XY Control) After the battery is hooked up and the power switch is depressed the XY control will be capable of operating the Elbow Mechanism and the shoulder mechanism simultaneously. The XY control is utilizing by moving the first digital joystick in any of its 8 directions. To activate the XY control, make sure that the Toggle switch that controls the X/Y mechanism is depressed. - Make sure the Toggle switch that controls the Wrist Mechanism is not depressed. 7) How to Control the Wrist Mechanism of the Assistive Robotic Arm 13

15 After the battery is hooked up and the power switch is depressed the Wrist Mechanism will be ready for operation. To change the Assistive Robotic Arm into wrist mode depress the wrist mode toggle switch. Figure Wrist Mechanism Toggle Switch The Wrist Mechanism is controlled by the Up/Down and the Right/Left controls of the first digital joystick. The Up/Down Motion enables the user to tilt the wrist up and down and the Right/Left Motion enables the user to pan the wrist from right to left. This will enable the user to be able to reach things that are very close to the table or desk and facilitate pick up objects of various shapes and sizes for the user. Figure Digital Joystick 1 14

16 The Wrist Mechanism consists of control will consist of two servo motors that are attached to each other so as to be capable of achieving pan and tilt motion of a camera. The wrist mechanism however will hold the gripper mechanism on top of it. The wrist mechanism will act to rotate the grabber based on commands from the client. This motion is important for manipulating objects and grasping horizontal objects. The wrist will pan and tilt 90 degrees and will be controlled by the joystick. In order to accomplish this, a camera adjustment pan tilt system will be used. Figure : Pan/Tilt Mechanism Attached to the Elbow Mechanism and the Gripper. 8) How to Control the Elevator Mechanism of the Assistive Robotic Arm The Elevator Mechanism is controlled by the second digital joystick. It moves up and down with the second digital joysticks and has built in limit switches so that the user does not have to worry about over stroking the motor. The Elbow Mechanism of the Assistive Robotic Arm consists of a linear actuator mounted upside down to the Round Servo Horn of the shoulder mechanism. The Linear Actuator is capable of rotating on its own. In order to prevent this, a guiding rod has been added to the design to inhibit its ability to rotate. 15

17 Figure : The Second Digital Joystick 9) How to Control the Gripper of the Assistive Robotic Arm The gripper of the assistive robotic arm is also controlled by the second digital joystick. If the arm is moved from right to left it will cause the gripper to close. If the second digital joystick is moved in the opposite direction it will cause the gripper to open. Figure : The Second Digital Joystick 16

18 2 Maintenance 2.1 Electrical Wiring In order to maintain electrical integrity of the robotic arm it is important to ensure that all electrical connections remain secure. This should be accomplished by regularly inspecting heat shrink and soldering connections. Step 1: Ensure power is off. Step 2: Remove orange protective enclosure by unscrewing set pin. 17

19 Step 3: Starting at the gripper end, inspect each wire and connection for signs of damage. Step 4: Follow wires down to base unit, ensuring that no wires or connections are damaged. 18

20 Step 5: Gently check that ribbon cable is not tangled and is firmly attached to both control box and arm base. Step 6: Return enclosure and fasten with pin. 19

21 2.1.2 Circuit Board To ensure reliable functioning of the electronic components of the robotic arm it is also necessary to occasionally check and clean the printed circuit board. Step1: Ensure power is off. Step 2: Carefully open base unit box utilizing the four screws on the top of the unit. 20

22 Step 3: Using compressed air clean any dust off of the circuit board. NOTE: never clean circuit board with liquid. Fig: Compressed Air Step 4: Verify that all connections are securely soldered to the circuit board. 21

23 Step 5: Verify that ribbon cable is securely fastened to ribbon socket on circuit board. Step 6: Carefully return cover to base unit box. 22

24 2.2 Mechanical In order to maintain proper mechanical functionality it is important to regularly remove protective enclosure and inspect gears and servo motors. Step 1: Power device off. Step 2: Carefully remove orange enclosure by removing set pin. Step 3: Carefully inspect gear boxes to ensure that all teeth are intact and nothing has become jammed into the gear mechanism. 23

25 Step 4: Carefully ensure that screws in elbow unit are tightened. Step 5: Carefully ensure that allen nut pictured is tight. 24

26 Step 6: Check set screws at the base of the linear actuator to ensure that they are tight. Step 7: Check allen nut in base servo. 25

27 Step 8: Verify that base screws are firmly attached to the mounting surface. Step 9: Return orange enclosure to upper arm, affix with pin. 26

28 Step 10: Return power switch to the on position. 2.3 Environmental It is important that the robotic arm not be subject to an inclement environment. The robotic assistive device is not meant to encounter an outdoor or wet environment. In order to ensure that the robotic device is always functioning it is important that the device is periodically cleaned. The following procedure should be followed approximately once a month. Step 1: Ensure that the device is powered off. 27

29 Step 2: Clean control box with disinfectant wipes. 28

30 Step 3: Remove orange enclosure by means of set pin. Step 4: Wipe down gripper and metal components with disinfectant wipes, be careful not to wet servos or electronics. Step 5: Return enclosure and power back on. 29

31 3 Technical Description 3.1 Gripper The gripper used is the Big Gripper purchased from Budget Robotics online catalog. Big Gripper measures 6" long, 2 3/4" wide and 1 1/4" thick (with servo the total thickness is 2"). Weight with servo is 3.7 ounces. Lifting capacity is 8-12 ounces, but is conservatively limited by the wrist mechanism you use, if any. Full-open to full-close of the fingers requires approximately 90 degrees of servo rotation. Figure 3.1.1: Big gripper The gripper is controlled by a servo motor connected through a push rod assembly. This assembly allows the rotational motion of the servo to be translated to a gripping motion. The attachment mechanism can be seen in the following figure. 30

32 Figure 3.1.2: Big gripper servo rod assembly. The gripper also contains mounting holes so that it can be easily attached to the body of the assistive robotic arm. Rubber cushions can be added over the length of the fingers so that the gripper can function more safely and can be grip smooth objects more effectively. Figure 3.1.3: Big gripper spacer and mounting hole assembly.\ 31

33 Figure 3.1.3: Fully assembled gripper with servo motor visible. 3.2 Wrist The wrist functions in a twist and tilt motion. These two degrees of freedom are accomplished through a pan tilt mechanism housing two servos. This mechanism is outlined in the following technical drawings. Figure 3.2.1: Pan tilt assembly side view. 32

34 Figure 3.2.2: Pan tilt assembly mounting plate The pan tilt assembly holds two servo motors. For this application we used the HS-475HB Super Pro Servo and the HS-645MG Ultra Torque Servo. The HS-645MG Ultra Torque was selected for the tilt mechanism as it requires a heavier load. The technical details for these servo motors can be found below. Figure 3.2.3: Hitec HS-645MG used for tilt mechanism HS-645MG Ultra Torque Detailed Specifications Control System: +Pulse Width Control 1500usec Neutral Required Pulse: 3-5 Volt Peak to Peak Square Wave Operating Voltage: Volts Operating Temperature Range: -20 to +60 Degree C Operating Speed (4.8V): 0.24sec/60 at no load 33

35 Operating Speed (6.0V): 0.20sec/60 at no load Stall Torque (4.8V): oz/in. (7.7kg.cm) Stall Torque (6.0V): oz/in. (9.6kg.cm) Operating Angle: 45 Deg. one side pulse traveling 400usec 360 Modifiable: Yes Direction: Clockwise/Pulse Traveling 1500 to 1900usec Current Drain (4.8V): 8.8mA/idle and 350mA no load operating Current Drain (6.0V): 9.1mA/idle and 450mA no load operating Dead Band Width: 8usec Motor Type: 3 Pole Ferrite Potentiometer Drive: Indirect Drive Bearing Type: Dual Ball Bearing Gear Type: 3 Metal Gears and 1 Resin Metal Gear Connector Wire Length: 11.81" (300mm) Dimensions: 1.59" x 0.77"x 1.48" (40.6 x 19.8 x 37.8mm) Weight: 1.94oz. (55.2g) The HS-475HB Super Pro Servo was used for the pan mechanism. The details on this servo are as follows. Figure 3.2.4: Hitec HS-475HB servo used for pan mechanism. Hitec HS-475HB Detailed Specifications Control System: +Pulse Width Control 1500usec Neutral Required Pulse: 3-5 Volt Peak to Peak Square Wave Operating Voltage: Volts Operating Temperature Range: -20 to +60 Degree C Operating Speed (4.8V): 0.23sec/60 at no load Operating Speed (6.0V): 0.18sec/60 at no load 34

36 Stall Torque (4.8V): 61 oz/in. (4.3kg.cm) Stall Torque (6.0V): 76 oz/in. (5.5kg.cm) Operating Angle: 45 Deg. one side pulse traveling 400usec 360 Modifiable: Yes Direction: Clockwise/Pulse Traveling 1500 to 1900usec Current Drain (4.8V): 8mA/idle and 150mA no load operating Current Drain (6.0V): 8.8mA/idle and 180mA no load operating Dead Band Width: 8usec Motor Type: 3 Pole Ferrite Motor Potentiometer Drive: Indirect Drive Bearing Type: Top Ball Bearing, Lower Bushing Gear Type: Karbonite Gears Connector Wire Length: 11.81" (300mm) Dimensions: 1.50" x 0.8"x 1.4" (41 x 20 x 37mm) Weight: 1.4oz (39g) 3.3 Elbow Mechanism The elbow mechanism consists of a HS 815BB servo contained in a power gear box. This set up allows for increased torque as well as increased side load capacity. This was particularly important for this joint as it allows for a rigid support of the upper arm, gripper and load. Fig 3.3.1: HS-815BB servo used for elbow mechanism. HS-815BB servo Detailed Specifications Control System: +Pulse Width Control 1500usec Neutral Required Pulse: 3-5 Volt Peak to Peak Square Wave Operating Voltage: Volts Operating Temperature Range: -20 to +60 Degree C Operating Speed (4.8V): 0.48sec/140 at no load Operating Speed (6.0V): 0.38sec/140 at no load 35

37 Stall Torque (4.8V): oz/in. (19.8kg.cm) Stall Torque (6.0V): oz/in. (24.7kg.cm) Operating Angle: 70 Deg. one side pulse traveling 400usec 360 Modifiable: Yes Direction: Clockwise/Pulse Traveling 1500 to 1900usec Current Drain (4.8V): 8mA/idle and 700mA no load operating Current Drain (6.0V): 8.7mA/idle and 830mA no load operating Dead Band Width: 8usec Motor Type: 3 Pole Ferrite Potentiometer Drive: Indirect Drive Bearing Type: Dual Ball Bearing Gear Type: All Heavy Duty Nylon Gears Connector Wire Length: 11.81" (300mm) Dimensions: 2.59" x 1.18"x 1.26" (66 x 30 x 57.6mm) Weight: 5.6 oz. (152g) To increase the power and rigidity of the elbow mechanism we utilized a HS-800 Series Servo Power Gearbox with a 5:1 ratio. This gives the servo a power of approximately 1,715 oz in. The technical details of the power gearbox can be found below. Figure 3.3.2: Power gearbox dimensions 36

38 Figure 3.3.3: Power gearbox dimensions. The installation of the servo motor into the power gearbox was accomplished by removing the internal potentiometer from the servo and soldering the internal circuitry to the external gearbox potentiometer. The soldered connections can be seen in the following image. Figure 3.3.4: External potentiometer attachment. 37

39 3.4 Linear Actuator The elevator mechanism consists of a linear actuator used to change the height of the XY plane. This enables objects to be lifted without spilling or tipping them. Figure 3.4.1: Extended linear actuator. The linear actuator operates at 12V DC while but can be operated at lower voltages. Since speed is not an important design constraint in the assistive robotic device the linear actuator will be run at 5V DC. In testing the linear actuator it was deduced that while it does operate slower at 5V DC than at 12 V DC it will operate at a lower noise level. This is very beneficial to the client because he will utilize the arm in a school setting and will cause fewer disturbances to the class if the linear actuator produces less noise. The linear actuator technical specifications and dimensions can be found in the table below under 6 inch stroke. 38

40 Figure 3.4.2: Linear actuator dimensions. The linear actuator was mounted using a custom built bracket. This bracket included elements to attach the upper arm and a pin to ensure the actuator did not freely rotate. 39

41 Bracket 1 Upper Arm Linear Actuator Bracket 2 Rotating Base Figure 3.4.3: Linear actuator mounting bracket. 3.5 Shoulder The shoulder mechanism consists of a servo contained in a gearbox. The servo chosen for this high load application was the HSR-599TG. This servo has a torque 417 oz-in which will be more than sufficient to rotate the assistive robotic arm. The servo motor has a full set of titanium gears which has almost 50 times the strengths of nylon gears. Because many servos are designed for low load applications, it is important that we purchase a high torque servo such as this one. 40

42 Figure 3.5.1: Servo Motor HSR-5995TG Figure 3.5.2: Titanium gears within HSR-5995TG The HSR-599TG will operate at 6V with a current drain of only 300mA while idle and 4.2 amps at a full stall. Due to the usage of a gearbox and the normal loads expected by the assistive robotic device, a full stall is not expected and a normal current drain of less than 3 amps is expected. The motor itself is a coreless metal brush motor capable of operation between 4.8 and 7.4 volts. The detailed specifications can be seen in the table below. HSR-5995TG Detailed Specifications Control System: +Pulse Width Control 1500usec Neutral Required Pulse: Volt Peak to Peak Square Wave Operating Voltage Range: Volts Operating Temperature Range: -20 to +60 Degree C (-68F to +140F) Operating Speed (6.0V): 0.15 sec/60 at no load Operating Speed (7.4V): 0.12sec/60 at no load Stall Torque (6.0V): oz-in. (24kg.cm) Stall Torque (7.4V): oz-in. (30kg.cm) Standing Torque (6.0V): oz-in. (31.2kg.cm) 5 degree deflection Standing Torque (7.4V): oz-in. (39kg.cm) 5 degree deflection 41

43 Operating Angle: 90 Deg. one side pulse traveling 400usec 360 Modifiable: Yes Direction: Clockwise/Pulse Traveling 1500 to 1900usec Idle Current Drain (6.0V): 3mA at stop Idle Current Drain (7.4V): 3mA at stop Current Drain (6.0V): 300mA/idle and 4.2 amps at lock/stall Current Drain (7.4V): 380mA/idle and 5.2 amps at lock/stall Dead Band Width: 2usec Motor Type: Coreless Metal Brush Potentiometer Drive: 6 Slider Indirect Drive Bearing Type: Dual Ball Bearing MR106 Gear Type: 4 Titanium Gears Connector Wire Length: 11.81" (300mm) Dimensions: 1.57" x 0.78"x 1.45" (40 x 20 x 37mm) Weight: 2.18oz (62g) The servo is then mounted underneath a round black servo horn which supports the linear actuator and the rest of the robotic arm. This connection can be seen in the following figure. Figure 3.5.3: Servo mounted underneath large servo horn. 42

44 3.6 Base Unit The robotic assistive device can be mounted on a table or wheelchair via the base unit clamp mechanism. This clamp was custom manufactured out of steel to fit a variety of clamping surfaces. The clamp consists of two large screws which tighten to the bottom of the table and a mounting area on the top of the table used to secure the shoulder servo. This can be seen in the following two figures. Figure 3.6.1: Base Unit with servo mounted. Figure 3.6.2: Base Unit Screws 43

45 3.7 Electronics The robotic assistive device is controlled by a PIC16F877 microcontroller. This controller is a 16 bit processor with the following technical specifications. Microcontroller Core Features: High performance RISC CPU Only 35 single word instructions to learn All single cycle instructions except for program branches which are two cycle Operating speed: DC - 20 MHz clock input DC ns instruction cycle Up to 8K x 14 words of FLASH Program Memory, Up to 368 x 8 bytes of Data Memory (RAM) Up to 256 x 8 bytes of EEPROM Data Memory Pinout compatible to the PIC16C73B/74B/76/77 Interrupt capability (up to 14 sources) Eight level deep hardware stack Direct, indirect and relative addressing modes Power-on Reset (POR) Power-up Timer (PWRT) and Oscillator Start-up Timer (OST) Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation Programmable code protection Power saving SLEEP mode Selectable oscillator options Low power, high speed CMOS FLASH/EEPROM technology Fully static design In-Circuit Serial Programming (ICSP) via two pins Single 5V In-Circuit Serial Programming capability In-Circuit Debugging via two pins Processor read/write access to program memory Wide operating voltage range: 2.0V to 5.5V High Sink/Source Current: 25 ma Commercial, Industrial and Extended temperature ranges Low-power consumption: - < 0.6 ma 3V, 4 MHz - 20 μa 3V, 32 khz - < 1 μa typical standby current 44

46 Figure 3.7.1: Pin Diagram for PIC16F577. Port B was utilized for the output of our pulse width modulation signals while Port D was utilized for the input of joystick and mode signals. In the following C code, all of the program decisions can be seen. 45

47 46

48 47

49 48

50 49

51 The microprocessor was integrated in a printed circuit board. The schematic and the PCB design can be seen here. Fig Electronics schematic 50

52 Fig Printed circuit board schematic 3.8 Controller The controller mechanism consists of two digital joysticks and two toggle switches. These can be seen in the following diagrams. Digital joysticks have been chosen for their reliability and the lack of fine motor control requirements. 51

53 The technical information of the joystick can be seen in the following diagram. Figure 3.8.1: Digital joystick schematic. 52

54 Trouble Shooting Mechanical Issues Problem: The gripper arm appears loose to the base unit. Symptoms: Occasionally, the upper arm may appear to be loose from the forearm. The symptoms of this problem include shaky performance and the ability to lift the front arm by hand from a resting position. This problem can be quickly and easily remedied with the following procedure. Required Tools Phillips head screw driver Step 1: Ensure that power is off. Step 2: Remove orange enclosure by removing pin. 53

55 Step 3: Find two screws below elbow joint Step 4: Using Phillips head screw driver tighten screws 54

56 Step 6: Return orange enclosure Step 7: Return power to on position. Problem: Upper arm slips when movement is attempted. Symptoms: When the joystick is moved appropriately, a noise is heard but the upper arm does not move or moves only slightly. This could be caused by a loose nut in the servo mount. Required Tools Allen wrench Step 1: Turn power on and allow servo to move to steady position. Step 2: Turn power off. 55

57 Step 3: Remove orange enclosure by removing pin. Step 4: Locate black allen nut on the under side of the elbow joint 56

58 Step 5: With arm in centered position carefully tighten black allen nut. Step 6: Return orange enclosure and affix with set pin. Step 7: Return power to on position and verify operation. 57

59 Problem: Shoulder joint servo appears to operate when joystick is used but arm does not move. Symptoms: When joystick is appropriately used the shoulder servo can be heard operating but the arm does not move or moves only slightly. Required Tools Allen wrench Step 1: Turn power on and allow servo to move to steady position. Step 2: Turn power off. Step 3: Locate black allen nut on the under side of the round black servo horn. 58

60 Step 4: With arm in centered position carefully tighten black allen nut. Step 7: Return power to on position and verify operation. Problem: Shoulder servo motor appears to be uncentered. Symptoms: When starting arm, the shoulder joint is not in the proper initial position. In addition, when moving arm the servo motor encounters difficulty at the ends of its appropriate range. This problem could lead to damage to the servo motor if not properly addressed. Required Tools Allen wrench Phillips head screw driver Step 1: Ensure that the power to the device is off. 59

61 Step 2: Using the allen wrench locate and loosen the two set screws located at the base of the linear actuator. Step 3: Remove large pin in front of linear actuator. Carefully remove the arm from the base unit. Be especially aware of the wires connecting the arm from the base unit to avoid damage. 60

62 Step 4: Using the Phillips head screw driver, remove the round servo horn from the base unit via the screws located in the center of the actuator mounting bracket. Step 5: Completely loosen black allen nut from servo gear. 61

63 Step 6: Carefully remove large metal gear from servo. Step 7: Turn exposed potentiometer to a center position. 62

64 Step 8: Power device on, do not touch joysticks. Servo motor may begin to turn. Turn exposed potentiometer slowly and carefully in the opposite direction of motor gear until servo stops turning. Step 9: Power device off and carefully return metal gear. Be very careful not to turn the potentiometer when replacing gear! Step 10: Tighten black allen nut with allen wrench. 63

65 Step 11: Return servo horn to servo and replace mounting screws. Step 12: Place linear actuator back into mounting hole and tighten set screws. Note: be sure to align linear actuator head so that set screws do not line up with through hole. 64

66 Step 13: Replace large pin in front of linear actuator. Be sure to properly secure orange enclosure. Step 14: Power on and verify operation. 65

67 Electrical Issues Problem: Arm does not function, pressing any joystick results in the same random motion. Symptoms: Even after powering off and on, the arm refuses to properly function. All joysticks and settings result in the same random movement. This is likely a microprocessor issue and must be verified. Note: this is an advanced problem and will require a trained professional with specialty equipment. Required equipment: Oscilloscope Multimeter Step 1: Remove four screws to expose electronics enclosure. Step 2: Turn power on and inspect microprocessor for heat or damage. 66

68 Step 3: Using multimeter verify that voltage of pins 11 and 32 is 5V with respect to ground and that pins 31 and 12 are grounded. If not, the microprocessor may be damaged and may need to be replaced. Before new microprocessor is replaced check and replace 7805 voltage regulator if necessary. Step 4: Using oscilloscope verify that pins 37 through 33 are all outputting a square wave with frequency of approximately 50hz. This square wave should vary in pulse width when joysticks are moved. 67

69 Step 5: If any of the above issues are found a serious electrical problem is present and the microprocessor will need to be replaced. Contact the Uconn Biomedical Engineering Department to receive a reprogrammed microprocessor. 68

70 References