TABLE OF CONTENTS LIST OF TABLES.............................................................................................................................. 3 LIST OF FIGURES............................................................................................................................ 4 1 SYSTEM COMPONENT DESCRIPTIONS ............................................................................... 5 1.1 BARRETTARM (BA4-310).......................................................................
5 BARRETTARM CABLE MAINTENANCE ............................................................................. 31 5.1 GENERAL ARM CABLE CIRCUIT DESCRIPTIONS ...................................................................... 31 5.1.1 FIRST-STAGE CABLE PATH DESCRIPTION ................................................................................ 32 5.1.2 SECOND-STAGE CABLE PATH DESCRIPTION ............................................................................ 33 5.2 HELPFUL TOOLS & TIPS ...........
LIST OF TABLES Table 1 - Safety Circuit fault conditions and results................................................................ 12 Table 2 - Header Designations on Motion Control Board ....................................................... 17 Table 3 - Base Switch SW1 .................................................................................................... 17 Table 4 - Filter Parameters .....................................................................................................
LIST OF FIGURES Figure 1 - BarrettArm BA4-310 ................................................................................................5 Figure 2 - BarrettWrist BW3-210..............................................................................................6 Figure 3 - Fault Status Indicator LEDs......................................................................................9 Figure 4 – Main Power Indicator LED ...............................................................................
1 System Component Descriptions 1.1 BarrettArm (BA4-310) The BarrettArm BA4-310 is a high-speed, 4-degree-of-freedom (4-DOF) manipulator with human-like kinematics. With its aluminum frame and advanced cable-drive systems, including a patented cabled differential, the BarrettArm is lightweight with no backlash, extremely low friction, and stiff transmissions. All of these characteristics contribute to its high-bandwidth performance.
1.2 BarrettWrist (BW3-210) Similar to the BarrettArm, the BarrettWrist utilizes various metal alloys and plastics to achieve its structural strength and lightweight. The servomotors for axes 4 & 5 (this discussion assumes the wrist is connected to the 4-DOF BarrettArm) are located at the base of the wrist to minimize their inertial effects on the host robot arm. The final roll joint in the BarrettWrist, motor axis 6, is the only geared axis.
1.3 BFC-200 Control Cabinet 1.3.1 Overview The electrical cabinet for the Barrett 7-DOF robotic system contains all of the servo, power, and signal processing hardware as well as the logic circuitry and hardware for the user/robot safety systems. Connections from the host computer to the servo current controllers and safety systems are also made through the control cabinet. The sturdy aluminum frame has a removable cover, providing access to the internal wiring.
WARNING: Always disable the motors before powering up the system and before resetting the safety fault logic. EMERGENCY STOP (Red) The Emergency Stop button permits the user to shut down the system manually. The E-Stop button will lock in the depressed position when pushed. The mushroom-head construction allows the user to activate the button quickly without needing to find the center of the switch in an emergency situation.
loss. This will require the 3-phase power to be cycled to clear the fault on the drive. Please refer to the Kollmorgen Servostar Installation and Setup Manual for a complete list of drive fault conditions. Over Velocity Fault – These lights are normally off and will come on to indicate a motor has moved faster than the desired maximum velocity. The desired maximum velocity can be set by adjusting the potentiometers in the row labeled Velocity Limits below their respective lights.
1.4 Electrical Power & Signal Cables 1.4.1 BA4-310 Signal Cables Communication between the host computer and the control cabinet is done through an adaptor box. This adaptor box interfaces three ribbon cables from the controller cabinet with five ribbon cables from the host computer. The connections between the controller cabinet and adaptor box consists of three, 50-pin ribbon cables. Two of the cables are used for resolver/encoder feedback from and command signals to the controllers.
BarrettArm. This cable provides power to and feedback from a BarrettHand mounted on a 7DOF BarrettArm system. 1.5 Host Computer The BarrettArm system has been tested with, and operates with, the following host computer: Dell Dimension XPS H266 (Pentium II) with 64M of RAM. Similarly configured PC computers from other manufacturers should also be sufficient. Barrett recommends using the fastest CPU available to the user for best performance.
Table 1 - Safety Circuit fault conditions and results Conditions Any of the motor controllers experience a controller fault. See section 7.1 of the Kollmorgen ServoStar Installation and Setup Manual. Any of the controllers exceed the predetermined velocity limits (over velocity fault) Logic power reduces to less than 4.4 V The Emergency-Stop button is pressed User I/O sends a low active signal from the computer. During system power-up. During system power-down.
mapping of signals from 5 cables from the PC/DSP controller board to 3 cables to the BFC-200 Control Cabinet, see Figure 5. Connections to Control Cabinet Connections to MEI Board Figure 5 – Adaptor Box Connections 2 Workspace Preparation 2.1 Power Source The standard BarrettArm system requires a 3-phase, 60 Hz, 220 VAC electrical supply capable of at least 20 amperes output.
Figure 6 - Lab Mounting-Surface Diagram The arm may also be mounted on a surface that is not horizontal (ex from a wall or ceiling). Keep in mind, however, that some of the BarrettArm’s pre-packaged software routine for gravity compensation will no longer function properly if the arm-mounting surface is not horizontal. 2.3 General Safety Proper precautions should be taken when selecting the location and setup of your BarrettArm system.
3 System Setup This section describes the steps required to interconnect the components of the BarrettArm system, power up the system, and perform some routine system checks. Do not proceed until the workspace has been prepared according to Section 1.7. Unless explicitly noted, all Section 3 instructions referencing the optional BarrettWrist can be ignored if the user is setting up only the 4-DOF BarrettArm. 3.
Figure 8 - BarrettArm Quick-Connect Photo 3.2 Motion Control Board (Installation & Setup) 3.2.1 Physical Installation • Turn the computer off, open the cover to access the motherboard, and ground your body to the chassis of the computer. • Unwrap PC/DSP board. • Set an I/O address on the board, which does not conflict with any other peripheral device (see details in Section 3.2.2). • Orient the board inside the computer so that it lines up with an unused, full length ISA bus slot.
Table 2 - Header Designations on Motion Control Board Motor Axes 0-1 Motor Axes 2-3 Motor Axes 4-5 Motor Axes 6-7 User I/0 Header P6 Header P7 Header P4 Header P5 Header P1 3.2.2 Hardware Address / Memory Mapping The DSP is mapped into the I/O space of the host CPU. Starting with the base I/O address the board uses 16 addresses in the computers I/O space. The default base address is 0x300.
Copy the Torque Ripple data from the disk labeled Torque Ripple Data to the directory :\btech\trdata\. 3.3 Electrical Connections 3.3.1 Main AC Power A 4-conductor AC power cable is provided to connect the control cabinet to a wall source. Connector details vary from customer to customer and will be determined during the preparation for installation. The wall source should be sized to supply 20 continuous AC amperes at 208-220VAC phase-to-phase and 50-60 Hz.
I/O Connector 1 I/O Connector 2 AC Power Motors 4-6 Signals Motors 0-3 Signals Motor 0-3 Power Motor 4-6 Feedback Motors 0/1 Feedback Motor 4-6 Power Motor 2/3 Feedback Figure 9 - Control Cabinet All BarrettArm and BarrettWrist power and signal cables from the Kollmorgen Controllers exit through the array of mil-spec circular connectors on the rear panel of the cabinet. To attach one of these 4.
Figure 10 - Ribbon Cable Sockets on the Motion Control Board 3.3.4 The BarrettArm Connections to the BarrettArm (and optional BarrettWrist & BarrettHand- if installed) are made at the back of the Arm base. Like on the cabinet rear panel, the connectors at the arm are circular connectors with ¼-turn locking rings. See Figure 11 for details. Barrett Technology, Inc. BA4-310 System User Manual Version 1.
Figure 11 - BarrettArm Electrical Connection Locations 3.4 System Startup You are now ready to start controlling the motors in the robot. Before C code is written, functionality of each of the motors should be verified. The motors can be verified using the Motion Console program supplied by Motion Engineering, Inc. Read through this entire section before beginning. • • • • • • • • • Read Chapter 6 – Motion Console Reference in Version 2.
• • • Set each of the axes as: servo axis, closed loop, and bipolar Verify all axes have an Abort Fault for the Axis Status. Enable the robot by pressing green Enable button on front of cabinet.
Table 5 - Point-to-Point Motion Sample Parameters Axis Delay st 1 Point nd 2 Point Velocity Acceleration 0 0 0 10000 10000 10000 3.4.2 Differential Axes: 1, 2 and 4, 5 Because the differential motor axes must act in coordination to produce motion in a single robot joint, verifying these motors is more difficult. Before proceeding with this section become familiar with the transforms that link motor space to joint space in Appendix B Motor-to-Joint Position Transformations.
specifies when to enable the robot. See the BarrettArm software manual for information on each of the demos. For your convenience the wamdemo program was compiled for 4 DOF (wamdemo4.exe), 7 DOF (wamdemo7.exe) and 7 DOF with Hand (wamdemoH.exe). Run the program that matches the system you are testing. Barrett Technology, Inc. BA4-310 System User Manual Version 1.
4 Overview of Cable Transmissions 4.1 Terminology Before this manual discusses the cabled transmissions in the BarrettArm or BarrettWrist, it will be helpful to define some general terms common to cabled systems. Cable – a “wire rope” typically made from very fine strands of stainless steel. The composite tensile strength and stiffness is very high in a stranded cable yet it maintains flexibility in bending.
Figure 12 - Pinion to Pulley Transition Types Pre-tension – cable tension, internal to a cable circuit, which is present even when the drive has no external loading. Pre-tension is added to eliminate backlash (in this case, cable slack) in the transmission. Tensioner – the mechanism in a cabled transmission, which applies and maintains pre-tension in the drive cables.
Figure 13 - Patented Cable Tensioner 4.3 Making Replacement Cables Pre-made cables can be ordered from Barrett Technology, Inc. Should the user desire to make their own cables, cable stock, terminations, and tools may also be purchased. However, Barrett Technology cannot be held liable for reduced performance limits of the BarrettArm due to installation of cables not pre-made and tested by Barrett. It is essential that only the recommended cables be used.
Table 6 - Arm Cable Specifications Qty. Cable Type Termination Type Length [mm(in)] Stage 2 2 4 2 2 1 1 2 1 1 1 1 2047 2054 2047 2054 2054 2047 2047 2054 2095 2095 2095 2095 405-B-3 405-B-4 405-B-3 405-B-4 405-B-4 405-B-3 405-B-3 405-B-4 415-B 415-B 415-B 415-B 1829 (72) 2692 (106) 2286 (90) 2286 (90) 2032 (80) 2159 (85) 1778 (70) 737 (29) 354±5 (13.9) 391±5 (15.4) 402±5 (15.8) 348±5 (13.
Table 8 – Wrist Cable Specifications Qty. Cable Type Termination Type Length [mm(in)] Stage 4 4 4 1 1 1 1 2019 2024 2047 2054 2054 2054 2054 401-B-1 401-B-1 401-B-3 401-B-3* 401-B-3* 401-B-3* * 401-B-3 965 (38) 610 (24) 559 (22) 96±5 (3.8) 106±5 (4.2) 132±5 (5.2) 152±5 (6.
1. Crimp the appropriate termination type onto one end of the cable being made. • Slide the correct size termination (rounded end first) over the annealed portion at the free end of the cable. Be sure to slide beyond the annealed (colored slightly blue or black) portion of cable. NEVER crimp a termination onto the annealed section of a cable. • Place the termination into the T-185 termination crimper (T-188 for 415-B terminations); crimp once lightly. • Rotate the termination 60° and crimp again.
5 BarrettArm Cable Maintenance 5.1 General Arm Cable Circuit Descriptions This section describes the parts of various cable circuits and the elements that they have in common. Subsequent sections explain how to replace worn drive cables as a part of standard BarrettArm maintenance. There are a total of 20 drive cables in the 4 degree-of-freedom BarrettArm. All four motor axes have similar cable circuits, each of which reduces the motor shaft speed in two stages.
Figure 14 - Typical Cable Circuit Arrangement 5.1.1 First-Stage Cable Path Description Motor shafts drive each 1st-stage through a special split pinion. All four motor split pinions are identical except for length. The motor pinion parts are called the inner motor pinion (with grooves for cable guidance) and the outer motor pinion (no grooves). The outer motor pinion can rotate relative to the inner pinion via the tensioner to add pre-tension to a cable circuit.
1st-stage cabling in the first three motor axes is similar. The cable attached to the inner motor pinion connects to the outside termination of the appropriate pulley. The cable attached to the outer motor pinion connects to the inside pulley termination. The two 1st-stage cables of the fourth motor axis span a large (~510 mm) distance down the inside of the inner arm link.
pinion, hold each wrap with your fingers to keep the cable from unwinding. At the end of each cabling step, one or two pieces of masking tape keep cables temporarily in place. Other helpful tools are listed in Table 11. Table 11 – Arm Cabling Tools Tool ½-inch masking tape Blunt tweezers 1-2 Rubber-tipped mild spring clamps 5/32” hex torque-driver 5.
5.3.1 2nd Stage [ ] 1. Form the two 2692mm 2nd stage cables into U-shapes without permanently bending the cables (i.e. do not kink the cable bend). The loose ends of each cable should be uneven by approximately 35mm. [ ] 2. Place joint 1 (base joint) in its center position between stops. The second-stage base pulley has two slots cut in the side of the pulley. These slots allow the second stage cable to enter the pulley and wrap around shoulder screws acting as loop-termination posts.
[ ] 3. Locate the horizontal slot at the top of the 2nd stage pulley surface. Feed the U-bend loop of one cable from right to left until the loop appears on the inner diameter of the pulley. Fit the U-bend around the termination post on the top flange. [ ] 4. Take the U-bend of the other cable and place it through the slot and around the termination post on the bottom flange. This termination leads the cable onto the bottom of the base pulley outside diameter.
[ ] 9. Being careful to keep the bottom-flange cable ends from crossing (i.e. top, shorter cable should remain the top cable at the transition from pulley to pinion). Insert the longer (bottom) cable-end’s brass lug into either of the two terminations at the top end of the left pinion. Wind on the longer cable 1/2 turn by rotating the pinion. Attach the remaining shorter (top) cable-end’s brass lug to the remaining termination at the top end of the left pinion.
which 2nd-stage pinion termination was used first). Be careful not to cross or kink the cable. While wrapping each turn, keep previous turns tight and in position with a finger or tape. Temporarily tape the cable wraps in place when done. [ ] 2. Take the free end of cable and connect its brass lug to one of the two terminations on the inner motor pinion. By rotating the motor pinion, wind the cable ½ turn through the second (unused) termination on the inner motor pinion.
[ ] 9. Finally, tension the cable circuit by adding a pre-tension slightly less than ½ the 1ststage cable’s breaking strength. This is accomplished by applying 0.68 N-m [96 oz-in] to the lubricated pre-tensioning set screw using the torque driver provided with your system, running the joint through its full range of motion, applying the specified torque again to remove the new cable slack, and repeating this process until moving the joint no longer reduces the tension in the cables (i.e.
5.5 Differential Input (J2 & J3, M1 & M2) NOTE: It is assumed in the following instructions that the differential output is already properly cabled. The cabling for these two circuits is identical, so references to motor axis 1 will be valid for axis 2 as well. The motor axes will be cabled one at a time. Each drives one input pulley of the cabled differential.
[ ] 6. Install the U-bend of the 2286mm cable into outboard termination loop slot such that the longer end rides on the outboard edge of the 2nd-stage pulley. Gently push the cable as far as possible into the slot. Place a piece of tape over the loop to prevent it from dislodging during cabling. Repeat for the inboard loop such that the longer end rides on the inboard edge of the 2nd-stage pulley. [ ] 7.
Figure 19 - Outboard Cable on 2nd-Stage Pulley [ ] 9. Using caution not to cross the parallel cable pair, attach the longer end of the outboard cable to either inboard termination slot of the right pinion as shown in Figure 20. Wind that cable end onto the pinion 1/2 turn. [ ] 10. Next, attach the other end of the outboard cable onto the remaining inboard termination slot of the right pinion. It is important that the cables NEVER cross during their track through the circuit.
[ ] 13. Next, attach the shorter end of the inboard cable into the remaining outboard termination slot of the left pinion. It is important that the cables NEVER cross during their track through the circuit. Check that the outer-most single cable of the pair on the pulley remains the outer-most cable on the pinion and that the innermost single cable on the pulley remains the innermost cable. This will insure proper cable path transitioning from the pulley to the pinion. [ ] 14.
[ ] 6. Take one end of the other 2286mm 1st-stage cable and attach the brass lug to the termination closest to the vertical support on the left pulley. [ ] 7. While this pulley remains immobilized wrap the cable 10 turns around the pulley. Be careful not to cross the wraps or damage the cable. While wrapping each turn, keep previous turns tight and in position with your fingers or a piece of tape. Temporarily tape the wraps in place when done. [ ] 8.
5.6 Elbow Joint (J4, M3) Although the M3 cable circuits are conceptually the same as for motor axes 0-2, the pulley/pinions and second-stage pulley for motor axis 4 look very different. For Joint 4, both pulley/pinions are on the same shaft and their pulley surfaces actually merge such that 1st-stage cables can wrap across the seam between them. The motor pinion is also separated from the rest of the transmission by the length of the inner arm link.
Figure 21 - Elbow Directional References 5.6.1 2nd Stage [ ] 1. Place joint 3 in the middle of its joint range if not already in this position. Move joint 4 such that the inner and outer link axes are inline (arm at full extension). [ ] 2. Form a U-shaped bend in the middle of one of the 737mm 2nd-stage cables without kinking it. As shown in Figure 22, fit this “U-bend” around the boss in the right 2ndstage pulley. It doesn’t matter which end goes over or under the boss.
Figure 22 - Right 2nd-Stage Elbow Pulley Cabling [ ] 3. Form a U-shaped bend in the middle of the other 737mm 2nd-stage cable. Fit this ‘Ubend’ around the boss in the left 2nd-stage pulley and tape as shown in Figure 23. Figure 23 - Left 2nd-Stage Elbow Pulley Cabling [ ] 4. Locate the two brass lugs of the right cable. Make sure that the cables do not cross anywhere along their path.
TIP: It is helpful to apply a piece of tape to prevent the lug from slipping out of the termination until the circuits are pre-tensioned. Wind on this cable a 1/2 turn by rotating the pulley/pinion. [ ] 6. Without crossing the cables, attach the remaining brass lug of this cable to the remaining 2nd-stage termination, located 180 degrees from the first termination. This cable end should be inboard of the cable end terminated in the previous step.
5.6.2 1st Stage [ ] 1. Place joint 3 in the middle of its joint range if not already in this position. To begin, joint 4 should still be positioned so that the elbow is folded flat against the inner arm link as shown in Figure 24. Figure 24 - Elbow Position for 1st-Stage Cabling [ ] 2. Place one brass lug of the 1778mm 1st-stage cable into the sidewall termination of the left 1st-stage pulley.
Figure 25 - Left 1st-Stage Elbow Pulley Cabling TIP: Light, blunt tweezers or needle-nose pliers are very useful for snaking the cables through the narrow clearances in the elbow. As each turn of cable is wrapped onto the pulley surface, make sure that it does not cross the previous wraps (this is difficult because part of this pulley surface is obscured by other parts of the joint). Apply tape to the set of wraps to keep them in place until pre-tensioning.
Figure 26 - Right 1st-Stage Elbow Pulley Cabling As each turn of cable is wrapped onto the pulley surface, make sure that it does not cross the previous wraps (this is difficult because part of this pulley surface is obscured by other parts of the joint). Apply tape to the set of wraps to keep them in place until pre-tensioning. Allow the remaining cable to exit through back of the elbow. [ ] 6.
Figure 27 - 1st-Stage Elbow Cables Through Arm Link [ ] 7. Using a rubber-tipped spring clamp, secure the pulley/pinions together to prevent unwanted rotations while the Joint 4 motor pinion is being cabled. [ ] 8. Still facing the arm from the right hand side, rotate joint 2 clockwise until it comes to rest on its stop. CAUTION !!!: Be sure that the free cable ends that were dropped through the internal guide are not damaged when joint 2 is rotated.
Figure 28 - Motor 3 Pinion-Access Hole [ ] 9. Remove the tensioner worm from the outer motor pinion. [ ] 10. Locate the free end of the longer cable and connect its brass lug to one of the two terminations on the inner motor pinion. Then, after skipping over the first groove, tightly and smoothly wind the cable onto the motor pinion by rotating the pinion until none of the cable slack remains (see Figure 29). Temporarily tape the cable and the inner motor pinion firmly so that they will not unwind.
Figure 29 - Elbow Motor Inner Pinion Cable Wraps [ ] 11. Place the brass lug at the free end of the remaining shorter cable into the termination slot on the outer motor pinion. Make sure the lug is fully seated in the termination, then, keeping the inner pinion stationary, wind the free cable onto the outer pinion with a right-hand pitch by rotating only the outer pinion. Maintain a slight axial force on the outer pinion during this step so that the seam between it and the inner pinion does not open.
[ ] 14. Finally, tension the cable circuit by adding a pre-tension slightly less than ½ the 1ststage cable’s breaking strength. This is accomplished by: applying 0.68 N-m [96 oz-in] to the lubricated pre-tensioning set screw using the torque driver provided with your system, slowly moving the joint through its full range of motion, applying the specified torque again to remove the new cable slack, and repeating this process until moving the joint no longer reduces the tension in the cables (i.e.
6 BarrettWrist Cable Maintenance 6.1 General Wrist Cable Circuit Descriptions The wrist has three distinct cabling circuits: (1) the input transmission right side, (2) the input transmission left side, and (3) the differential. The input transmission left and right circuits are stages of gear reduction for the main motors in the base of the wrist. The differential circuit translates the rotation of the left and right side circuits into the main pitch and roll motion of the wrist.
tools and cable parts have been gathered prior to any cabling activities, and good safety precautions such as eye protection are utilized. The cabling instructions have numbered checkboxes next to each step for tracking progress. These pages may only be photocopied for use as a cabling checklist. Allow roughly 6 hours to cable the entire wrist for the first time. Subsequent cabling of the wrist after the user is familiar with the instructions can be completed in fewer than 2½ hours.
Differential Top Level #2 Cable Level #1 Cable Level #3 Cable Horizontal Steps Vertical steps Level #4 Cable Differential Bottom Figure 31 - Wrist Differential Cable Circuits [ ] 1. Remove both worms (set screws) from the worm gear tensioners, which are integrated into two of the vertical steps. Set them aside. [ ] 2. Begin with the Level #1 cable (the shortest length cable). Insert one end of the cable to the termination in the smallest diameter horizontal step in the differential top. [ ] 3.
[ ] 8. Bring the Level #3 cable around ½ turn on its horizontal step, then wrap over onto the vertical step of the same diameter and insert the free end into the termination on that step. [ ] 9. Put one termination lug of the Level #4 cable into the termination in the final horizontal step. Wrap the cable around ½ turn, then over to the largest vertical step. [ ] 10.
Figure 32 - Left Side 3rd-Stage Cabling [ ] 1. Begin with a 559mm 3rd-stage cable. Attach one end to the top termination in the upper 3rd-stage pulley. [ ] 2. Wrap the cable around the pulley 2 times using tape to hold the wraps if necessary. [ ] 3. Transition over to the left side pinion using a cross-wrap (the split in the surface of the left side pinion is closer to the top of the wrist that that on the right side). Attach the free end of the cable to the bottom termination of the pinion.
6.4.1.2 2nd Stage The cabling circuit for the second stage is represented in Figure 33. Figure 33 - Left Side 2nd-Stage Cabling [ ] 1. Begin with a 610mm 2nd-stage cable. Attach one end to the top termination of the left 2nd-stage pulley. [ ] 2. Wrap the cable around the pulley 2 times, using tape to hold the wraps if necessary. [ ] 3. Transition over to the left 2nd-stage pinion using an open-wrap. Attach the free end of the cable to the bottom termination of the pinion.
6.4.1.3 1st Stage The cabling circuit for the first stage is represented in Figure 34. Figure 34 - Left Side 1st-Stage Cabling [ ] 1. Remove the tensioner worm from the outer motor pinion on the left side of the wrist. [ ] 2. Begin with a 965mm 1st-stage cable. Attach one end to the top termination of the left 1st-stage pulley. [ ] 3. Wrap the cable around the pulley 2 times, using tape to hold the wraps if necessary. [ ] 4. Transition over to the left 1st-stage pinion (motor pinion) using an open-wrap.
[ ] 9. Insert the tensioner worm back into the motor pinion. To reach the worm bore, the user may have to rotate the wrist axes slightly to bring it around into view. Be careful not to lose tension in the 1st-stage cable at this point, as your work will unwind back through the 3rd-stage. Tighten the worm with the torque-driver to 0.23 N-m (32 oz-in). [ ] 10. Pre-tension the circuit according to Section 6.4.3 6.4.
6.4.2.2 2nd Stage [ ] 1. Begin with a 610mm 2nd-stage cable. Attach one end to the top termination of the right 2nd-stage pulley. [ ] 2. Wrap the cable around the pulley 2 times, using tape to hold the wraps if necessary. [ ] 3. Transition over to the right 2nd-stage pinion using an open-wrap. Attach the free end of the cable to the bottom termination of the pinion. Slowly and evenly wind on the cable by rotating the pinion until the cable is tight. [ ] 4.
[ ] 7. Wrap the cable around the pulley 8 times using tape to hold the wraps if necessary. [ ] 8. Transition over to the right 1st-stage pinion using an open-wrap. Attach the remaining free end of the cable to the top (outer) termination of the pinion (which houses the tensioner) and rotate the top segment of the pinion only. Maintain a slight axial force on the outer pinion during this step so that the seam between it and the inner pinion does not open.
Figure 35 - Proper Position of Wrist Cables for Pre-Tensioning The left and right circuits of the input transmission, with their three stages of reduction, require extra attention during pre-tensioning. The procedure for both the left and right cabling circuit begins by tightening the worms to 0.23 N-m (32 oz-in) until the cables in the first stage are taut. Then carefully back-drive the wrist through a full cycle and back again.
Appendix A - Denavit-Hartenberg Frames Z7 l7 X7 Z5 Z6 X5 X 6 l4 d4 Z3 Z4 X3 X4 l3 d3 Z0 Z1 Z2 Back of Robot X0 X1 X2 Figure 36 - Denavit-Hartenberg Frames Barrett Technology, Inc. BA4-310 System User Manual Version 1.
Figure 36 shows the entire 7-DOF BarrettArm system in the zero position. A positive joint motion is based on the right hand rule for each axis. The ‘Back of the Robot’ label points to the portion of the base where the connectors exit. The link parameters that were derived from Figure 36 are located in Table 13.
Appendix B - Motor-to-Joint Position Transformations The following transformations show the change in joint positions as a function of motor positions. The input transmission ratios and the differential transmission ratios are calculated from known pulley, pinion, and cable diameters.
N 5 10.27 N6 N5 n = 1 6 N 14.93 7 Equation 6: Wrist transformation ratios The motor position can also be derived from joint space by taking the inverse of the multiplying matrix.
Appendix C - Motor-to-Joint Torque Transformations Similar to the position transformations the following equations determine the joint torque from the motor torque.
1 2N5 M τ 4 1 Mτ 5 = Mτ 2 N 5 6 0 − n6 2N5 n6 2N5 0 0 Jτ 5 0 Jτ 6 − 1 Jτ 7 N 7 Equation 12: Wrist Joint-to-Motor torque transformations Barrett Technology, Inc. BA4-310 System User Manual Version 1.
Appendix D - Forward Kinematics The forward kinematics of the 7-DOF BarrettArm system is used to determine the end tip location and orientation. Each of the following transforms describes Joint k to Joint k-1. These transformations are calculated using the parameters in Table 13 and the matrix in Equation 13.
c6 0 5 Τ6 = -s 6 0 - s6 0 − c6 0 0 1 0 0 0 0 0 1 0 c7 - s7 0 0 − 1 L7 0 6 Τ7 = s 0 0 c7 7 0 0 0 1 The the forward kinematics are determined for any joint on the robot by mulitplying all of the joint transforms up to and including the final joint. To determine the end tip location and orientation use the following equation: 0 Τ7 = 0 Τ11 Τ2 2 Τ3 3 Τ4 4 Τ5 5 Τ6 6 Τ7 Equation 14: End tip position and orientation equation Barrett Technology, Inc.
Appendix E - Integration of Optional BarrettHand (BH8-250) The BarrettHand can be readily integrated into the 7-DOF BarrettArm system. There are two methods by which Hand control can be integrated with Arm control. The first method allows the user to control the Hand from a separate window while the Arm is running. The second method is integration of hand commands with Arm commands within the same program.
compiler, or the directory where ‘stdc.lib’ resides needs to be put into your compiler. Barrett has successfully integrated both Hand and Arm commands into the same program using Microsoft Visual C++ version 1.52. An example of this integration can be found in :\btech\source\wamdemo\wamdemo.exe Barrett Technology, Inc. BA4-310 System User Manual Version 1.
