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Barrett WAM Arm User Manual

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WAM
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User's Manual
Document: D1001
Version: AH.00

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  • Page 1: Table Of Contents

    User’s Manual Document: D1001 Version: AH.00...

  • Page 2: Table Of Contents

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Table of Contents TABLE OF CONTENTS ....................... 1 TABLE OF CONTENTS ....................... 2 LIST OF FIGURES........................4 LIST OF TABLES.......................... 5 LIST OF EQUATIONS ......................... 5 SYSTEM DESCRIPTION ..................... 6 WAM S ................. 6...
  • Page 3 WAM Arm – User’s Manual support@barrett.com www.barrett.com 4.5.2 Safety Board ......................29 WAM COMMANDS LIST....................30 WAM PROPERTIES LIST....................31 ..................... 31 OMMON ROPERTIES ......................36 OTOR ROPERTIES ..................42 AFETY ODULE ROPERTIES ....................45 EY TO ROPERTY ABLE CANBUS COMMUNICATION SPECIFICATIONS ............46 ...................

  • Page 4: List Of Figures

    WAM Arm – User’s Manual support@barrett.com www.barrett.com List of Figures 1 - WAM A ........................7 IGURE 2 - B ......................8 IGURE LANK UTER 3 - E ................ 8 IGURE LATES OF RIST AND UTER 4 – H ........................9...

  • Page 5: List Of Tables

    WAM Arm – User’s Manual support@barrett.com www.barrett.com List of Tables 1 – WAM C ................22 ABLE OMMUNICATION ETTINGS 2 – H ............22 ABLE OMMUNICATION AND OWER ETTINGS 3 – DC P ................... 23 ABLE OWER EQUIREMENTS 4 – 4-DOF WAM ) ....

  • Page 6: System Description

    The compactness, low system weight, and extraordinarily low power consumption make the WAM arm uniquely portable and so an ideal choice for use with mobile platforms. Its low mass and the absence of a controller cabinet ensure that it is significantly easier to mount than robotic arms of the same size.

  • Page 7: Wam Arm

    J1 through J4, and four brushless DC motors labeled M1 through M4. M1 controls the yaw (J1) of the WAM and is located in the base of the WAM. Using Barrett’s patented cable differential, M2 and M3 together control the pitch (J2) and roll (J3) of the WAM, and are contained in the shoulder of the WAM.

  • Page 8: Tool-End Attachments

    Barrett Hand, the wiring can simply be pushed inside the large open cavity. If using the Wrist without the Barrett Hand, the wires should be coiled neatly in the small cavity and the Wrist Plug installed to keep the wires from getting pinched.

  • Page 9: Figure 4 - Haptic Ball

    (if neither the Outer Link nor Wrist modules are installed). It provides a flat base that can be used to attach parts other than the ones designed by Barrett. The Tool Plate has four M6 tapped holes, evenly distributed in a circle, a 6-mm diameter dowel-pin hole, a quick-connect pin hole and slot, and two holes to connect the CAN Termination (see Appendix B for Tool Plate hole labels and dimensions).

  • Page 10: Power Supply

    The WAM Arm system comes with two safety pendants: a control pendant and a display pendant (shown in Figure 8). Both pendants show the present safety status of the WAM Arm, with status lights for the velocity, torque, voltage, and heartbeats of the robot. There is also a 7-segment LED single-character display which shows additional information related to any existing errors.

  • Page 11: Electrical Cables

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 1.1.7 Electrical Cables All necessary electrical cables are included with the basic WAM System, shown in Figure 9. An AC Line Cord connects the Power Supply to a wall source. A blue DC Power Cable connects the Power Supply or another DC power source to the WAM.

  • Page 12: Figure 10 - Maintenance Kit

    WAM Arm – User’s Manual support@barrett.com www.barrett.com • 1 Pair of Tweezers • 2 Clamps (for clamping the WAM to a table top) • 1 Roll of 13-mm (1/2”) Masking Tape • 1 Roll of Kapton Tape • 1 Slotted Screwdriver •...

  • Page 13: System Options

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 1.2 System Options 1.2.1 WAM Wrist The WAM Wrist module, shown in Figure 11, replaces the outer link of a four-degree-of-freedom WAM, adding joints 5, 6, and 7, for another three degrees of freedom. Mechanical and electrical quick-connect features make it easy to swap between the WAM’s outer link and the Wrist module...

  • Page 14: Passive Gimbals

    A vertical bar grip comes standard and is designed primarily for life-size haptics, exercise, and rehabilitation; but other grip and mounting options are available. The gimbals use Barrett Technology’s quick-connect system so that it may easily be interchanged with other end effectors.

  • Page 15: External Wam Pc

    1.2.3 External WAM PC Barrett Technology offers an external PC (see Figure 14) for advanced control applications that require more processing power or more memory than the WAM’s internal PC can provide. A standard keyboard and mouse, CANbus cable, and 2-m AC line cord are provided for use with the external PC.

  • Page 16: Control Software/Firmware Upgrades

    Control Software/Firmware Upgrades Barrett Technology releases software and firmware upgrades periodically (see Section 4.5 for details on firmware upgrades). Upgrades are available free of charge for customers of Barrett’s support subscription service. Customers with an expired support contracts can choose to renew their contract, or purchase the upgrades separately.

  • Page 17: Safety System: Pendants

    (also resulting in a braking effect), and they will ignore any command torque sent to them. To put the WAM Arm into the IDLE state (which will also reset any existing faults), press and hold the Shift button on the control pendant, then press the Reset/Idle button (yellow) and release both buttons.

  • Page 18: Handling Safety Faults

    This fault is cleared by pressing Shift-Idle on the control pendant. Placing the WAM Arm into the IDLE state applies a DC voltage on the motor bus and clears the fault. If the voltage approaches the limits, the voltage warning light is lit. If the voltage exceeds the limits, the voltage fault light is lit.

  • Page 19: System Setup

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Error occurs in state E-STOP IDLE ACTIVE Velocity exceeds VL1 No action Warn Warn Velocity exceeds VL2 No action Fault, E-STOP Fault, IDLE, Wait 1/4s Torque exceeds TL1 Warn for non-zero Warn for non-zero...

  • Page 20: Grounding

    Additionally, it is preferable that the metal chassis of the External Power Supply, the metal chassis of the Barrett Hand Supply (if applicable) and the WAM chassis are not in electrical contact with each other. If this is not possible, contact Barrett Technology for instructions.

  • Page 21: Figure 20 - Wrist Connector

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Alignment Pins D-sub connector Figure 20 – Wrist Connector Figure 21 – Separating the Outer Link Rotate ring this direction to remove Outer Link or Wrist Rotate ring this direction to attach Outer Link or Wrist Figure 22: Close-up of Outer Link connection ©...

  • Page 22: Safety Board Settings

    Figure 24 – WAM Backplate Figure 25 – Safety Board Cover Contact Barrett for additional modes of operation, for example: running 2 WAMs off of a single PC-104, or running a BarrettHand off of internal power with external (non-PC-104) communications.

  • Page 23: Electrical Connections

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 3.6 Electrical Connections 3.6.1 Power Source For applications using a standard (50-60 Hz, 100-120 or 200-240V) AC outlet: • Place the Power Supply on a flat, secure surface and verify that the Power Supply is OFF.

  • Page 24: Communications

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 3.6.3 Communications You can control the WAM over wired Ethernet, wireless Ethernet, or CANbus. Wired/Wireless Ethernet If you are using wired Ethernet to communicate between your personal computer and the internal WAM PC, attach the Ethernet cable from the network port on the WAM to a port on an Ethernet switch or hub.

  • Page 25: Code Examples

    These examples are preloaded onto the WAM PC to help demonstrate the capabilities of the WAM Arm and the functionality of the WAM library. The examples and their functions are as follows: Example 1: A minimalist program for the WAM that prints out the position of the end point of the WAM.

  • Page 26: Pc & Control Software

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 4 PC & Control Software 4.1 Library Overview This provides a brief overview of the WAM library. It is not an exhaustive feature list, but it gives a sampling of the WAM library’s functionality.

  • Page 27: File System Layout

    4.2 File System Layout The Barrett Technology robot control client software (btclient) is divided into multiple parts: examples/ - example source code for robot control software development doc/ - source code documentation, Doxygen (HTML/RTF) **...

  • Page 28: Updating Firmware

    (the wireless router is mounted on the outside). If you are trying to update a WAM without the above characteristics, or you need to download some of the files mentioned in the following steps please see instructions on the Barrett wiki at: http://wiki.barrett.com/index.php/Firmware_update_instructions.

  • Page 29: Safety Board

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 4.5.2 Safety Board 1. Ensure that main power to the WAM is off. 2. Remove the wrap-around base cover by releasing the four latches that secure it to the back plate of the WAM.

  • Page 30: Wam Commands List

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 5 WAM Commands List For the full WAM Application Programming Interface (API), please refer to the fully indexed and cross-referenced doxygen-style documentation in the btclient/doc/html directory. getProperty Command: Get Property Name: Obtains the properties of a single Puck™.

  • Page 31: Wam Properties List

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 6 WAM Properties List 6.1 Common Properties These properties are common to both the motor encoders and the Safety Module. Property: ADDR Address to peek/poke Definition: Values (Units): Read/Write: Default: Saved: Notes: Property:...
  • Page 32 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: DIG1 Digital I/O Definition: -1, 0, 1 Values (Units): Read/Write: Default: Saved: 0-3.3 V only (no optical isolation, reverse voltage, or overvoltage protection, Notes: be careful). -1 = Input, 0 = Output low, 1 = Output high, Pin 43 (Pin 44 =...
  • Page 33 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: IMOTOR Definition: Values (Units): Read/Write: None Default: Saved: Notes: Property: LOAD Load a property from non-volatile memory into active puck memory via the Definition: CAN bus Values (Units): Read/Write: None Default: Saved:...
  • Page 34 Saved: The standard Puck is designed for operation between 18V and 90V. However, Notes: contact Barrett Technology if operating the bus at a voltage other than 48 V. © 2008 Barrett Technology®, Inc. Document: D1001, Version: AH.00 34 of 80...
  • Page 35 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: VERS Firmware version (or the monitor version, if the Puck™ is in reset) Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: VLOGIC Definition: Values (Units): Read/Write: Default: Saved: Not yet implemented Notes:...

  • Page 36: Motor Properties

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 6.2 Motor Properties These properties are used only by the motor controllers (not the safety module). Property: ACCEL Definition: Values (Units): Read/Write: 2048 Default: Saved: Notes: Property: 32-Bit Close Target Definition: Values (Units):...
  • Page 37 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: HALLH 32-Bit Hall History Bitfield Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: HALLS Hall feedback bitfield: CBA Definition: Values (Units): Read/Write: Default: Saved:...
  • Page 38 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: IOFST Current Offset Calibration Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: IPNM The puck torque unit to Nm (Command Current / Nm) conversion is stored Definition: here Values (Units): Read/Write: 2755...
  • Page 39 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: LCVC Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: LFLAGS Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: 32-Bit Mechanical Angle in ENCODER counts?
  • Page 40 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: Counts/ms Definition: Values (Units): Read/Write: 1500 Default: Saved: Notes: Property: Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: The maximum torque a Puck™ will apply, even if commanded to apply more Definition: (in milliamps).
  • Page 41 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: PIDX Puck™ Index for Torque Definition: Values (Units): Read/Write: Default: Saved: Notes: Property: POLES Number of magnets on rotor Definition: Values (Units): Read/Write: 12, 8, or 6, depending on motor type Default:...

  • Page 42: Safety-Module Properties

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 6.3 Safety-Module Properties The Safety Module is an additional Puck located in the base of the WAM (not attached to a motor). The Safety Module has a puck ID of 10, and is identified in the software as SAFETY_MODULE.
  • Page 43 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: VL1, VL2 VL1 is the minimum velocity that will cause a warning; VL2 is the minimum Definition: velocity that will cause a fault. (rad/s or m/s) Values (Units): Read/Write: 0.5, 1.0 (respectively)
  • Page 44 WAM Arm – User’s Manual support@barrett.com www.barrett.com Property: ZERO After sending the pucks their known initial position, set the safety system's Definition: ZERO property to 1 so it can start calculating Cartesian velocities. Values (Units): Read/Write: Default: Saved: Use the DefineWAMpos() function in src/btwam/btwam.c to set the initial Notes: positions of the other motor controllers.

  • Page 45: Key To Property Table

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 6.4 Key to Property Table 45 MV 91 IKP Key Param. VERS 46 MCV 92 IKI ROLE 47 MOV 93 IKCOR 48 P 94 HOLD 49 P2 95 TIE ERROR 50 DP 96 ECMAX...

  • Page 46: Canbus Communication Specifications

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 7 CANbus Communication Specifications 7.1 Data Link Specifications 1Mbaud CANbus 8 time quanta per bit 75% sampling point Sync jump width = 1 time quanta (TQ) 11-bit MsgID (standard CAN) Proprietary protocol, not DeviceNet or CANopen Recommended reading: Controller Area Network by Konrad Etschberger 7.2 CANbus Timing...

  • Page 47: Canbus Frame Data Payload

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 7.4 CANbus Frame Data Payload 7.4.1 Standard CANbus Message Format CAN specifies a maximum of 8 bytes/frame payload – our typical payload consists of 4-6 bytes: [APPPPPPP] [00000000] [LLLLLLLL] [mmmmmmmm] [MMMMMMMM] [HHHHHHHH] A: Action, 0 = Get property, 1 = Set property P: Property (128 possible values, 0..127, 0000000..1111111), see Motor Controller Properties and...

  • Page 48: Full Communication Example

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 7.5 Full Communication Example This example contains: • 3 motors with IDs of 5, 6, and 7 • A host with an ID of 0 Host sends: MsgID [10000000000] → Group 0 Data [10000101] [00000000] [00000010] [0000000] → Set property 5 (STAT) to 2...

  • Page 49: Troubleshooting

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 8 Troubleshooting 8.1 Checking the Error Log One of the first steps to diagnosing many WAM problems is to examine the error log file /var/log/syslog. Here is a normal startup log for a 7-DOF WAM: Jul 29 20:27:41 WAM WAM: ...Starting btdiag program...

  • Page 50: Common Problems

    Jul 29 20:27:45 WAM WAM: WAMControl period Sec:0.002000, ns: 2000000 8.2 Common Problems The symptoms repeated in this section were either generated by Barrett’s own lab WAMs or were reported by Barrett’s customers. Problem: Can not log in to the WAM PC Reason(s): 1.
  • Page 51 WAM Arm – User’s Manual support@barrett.com www.barrett.com i) Attach the Puck serial cable to the safety board to verify that the safety puck is functional. Could it have overheated? 2. You are accessing data outside of the program’s memory space (not likely with standard example programs).
  • Page 52 The cable should be replaced before further use. 2. A brass termination slipped off the end of the cable. Solution(s): a) This is a manufacturing defect. Contact Barrett to get the cable replaced. © 2008 Barrett Technology®, Inc. Document: D1001, Version: AH.00 52 of 80...
  • Page 53 Reason(s): 1. An electrical component burned up. Solution(s): a) Carefully record all events leading up to the failure. Contact Barrett for repair. Problem: The WAM returns to home position before starting a new trajectory. Reason(s): 1. The first point in the trajectory is the home position.
  • Page 54 Solution(s): a) On-line calibration (either static or dynamic) can yield better data than the model. Barrett is working on calibration software and will notify the WAM User List when it is released. 4. Electrical wiring stiffness requires additional joint torque to overcome pulling effect near...
  • Page 55 WAM Arm – User’s Manual support@barrett.com www.barrett.com a) Reduce the payload. Remember that you must take into account accelerated loads while staying under the max payload specification. For example, the max payload for the 7DOF is 3 kg. This means you can accelerate 1.5 kg at 2G. Or you can hold 3 kg statically at the max reach.

  • Page 56: Theory Of Operation

    WAM system. The control loop is the repeated reading of motor angles and commanding of motor torques to provide a smooth and safe motion of the WAM Arm robot. High-level command is deciding when and where to move to robot and providing an interface for the user of the WAM system to accomplish their task.

  • Page 57: Chematic

    WAM and cause the motors to resistively brake if it senses a dangerous situation (see Section 2.2). Barrett Technology has created specially designed motor controllers called “Pucks™”, which are mounted directly to the motors they control. A Puck™ serves as a power source for the motors and commands a smooth, continuous torque based on the digital torque command.

  • Page 58: Kinematics, Transmission Ratios, And Joint Ranges

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 9.2 Kinematics, Transmission Ratios, and Joint Ranges 9.2.1 4 DOF and 7 DOF A good introduction to coordinate frames, transformations and kinematics is beyond the scope of this document. There are several good introductory robotics books available. We recommend Spong, M.;...

  • Page 59: Dimensions And D-Hframes

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Figure 36 – WAM 7-DOF dimensions and D-H frames Figure 36 shows the entire 7-DOF WAM system in the zero position. A positive joint motion is based on the right hand rule for each axis. Figure 37 through Figure 43 on the following pages show explicitly each of the seven joint kinematic parameters and joint limits.

  • Page 60: Rames And Limits

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Figure 37 – WAM Arm Joint 1 Frames and Limits Figure 38 – WAM Arm Joint 2 Frames and Limits © 2008 Barrett Technology®, Inc. Document: D1001, Version: AH.00 60 of 80...

  • Page 61: Rames And Limits

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Figure 39 – WAM Arm Joint 3 Frames and Limits Figure 40 – WAM Arm Joint 4 Frames and Limits © 2008 Barrett Technology®, Inc. Document: D1001, Version: AH.00 61 of 80...

  • Page 62: Rames And Limits

    WAM Arm – User’s Manual support@barrett.com www.barrett.com +`1.24rad - 4.76rad (+71 (-273 Figure 41 – WAM Arm Joint 5 Frames and Limits Figure 42 – WAM Arm Joint 6 Frames and Limits © 2008 Barrett Technology®, Inc. Document: D1001, Version: AH.00 62 of 80...

  • Page 63: Rames And Limits

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Figure 43 – WAM Arm Joint 7 Frames and Limits © 2008 Barrett Technology®, Inc. Document: D1001, Version: AH.00 63 of 80...

  • Page 64: Able 4 - 4-Dof Wam Frame Parameters With Blank Outer Link Installed )

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Equation 1 below gives the transform between two adjacent D-H coordinate frames. The D-H parameters that were derived from this equation are located in Table 4 and Table 5 below. Note that c and s stand for cos and sin respectively.

  • Page 65: Table 6 - Joint Limits

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Each of the joints has a mechanical stop that limits the motion. Refer to Table 6 below for a complete listing of the joint limits for each axis. Table 6 – Joint Limits...

  • Page 66: Dof With Gimbals

    A 4-DOF WAM Arm can be outfitted with optional 3-axis non-motorized gimbals that give precise angular feedback. The kinematics of the first 4 joints is identical to a 4-DOF WAM Arm. The kinematics for the additional 3 axes is shown in Figure 44.

  • Page 67: Able 7 - 4-Dof Wam + Gimbals Dh Parameters

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Figure 44 shows the WAM Gimbals in the zero position. A positive joint motion is based on the right hand rule for each axis. The D-H parameters that were derived from Figure 44 are located in Table 7 below.

  • Page 68: Motor-To-Joint Transformations

    WAM Arm – User’s Manual support@barrett.com www.barrett.com 9.2.3 Motor-to-Joint Transformations 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.

  • Page 69: Equation 10 - Arm Motor-To-Joint Torque Transformation

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Motor-to-Joint Torque Transformations Similar to the position transformations the following equations determine the joint torque from the motor torque: − ⎛ ⎞ τ τ ⎛ ⎞ ⎛ ⎞ ⎜ ⎟ ⎛ ⎞ ⎜...

  • Page 70: Appendix Aintegrating A Barretthand

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Appendix A Integrating a BarrettHand™ The BarrettHand can be readily integrated into the WAM system. The Hand can be powered either internally using the built-in DC-DC converter on the Safety Board, or externally using the standard BarrettHand power supply.

  • Page 71: Appendix Btechnical Specifications

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Appendix B Technical Specifications Kinematics Total number of joints: 4 or 7 Total number of motors: 4 or 7 Total joint friction: 3 Nm Mechanical stiffness: 1.5*10 Control stiffness: 5000 N/m Percent backdrivability: >...

  • Page 72: Wam Dimensions

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Cables AC Line Cord DC Power Cable Pendant Cables (Two) Ethernet Cable External CAN cable (optional) External Hand control cable (optional) Available Options 3-DOF Wrist 3-DOF Gimbals External Computer WAM Dimensions NOTE: The dimensions for a 4 degree of freedom WAM are the same except that the 4 degree of freedom WAM does not have a joint at 850 mm and the “End Plate”...

  • Page 73: Figure 46 - Tool Plate Dimensions

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Figure 46 – Tool Plate Dimensions US Patents (and international equivalents) 4,903,536 4,957,320 5,046,375 5,207,114 5,388,480 5,501,498 D351,849 D352,050 Additional US and international patents pending © 2008 Barrett Technology®, Inc. Document: D1001, Version: AH.00...

  • Page 74: Appendix Cfaq

    What types of motions are possible with the WAM Arm, and what mechanisms are used to control them? The WAM Arm has a workspace that can be approx a sphere 1 meter in diameter centered between the WAM’s “shoulders”. It can reach any position and orientation that does not require the arm to intersect with itself or some obstacle in a workspace ____.

  • Page 75: Table 9 - Maximum Torque (Mt) Ma To Nm Conversion Table

    WAM Arm – User’s Manual support@barrett.com www.barrett.com • Optical Encoders – When the WAM is first powered on, the motor controllers use Hall-effect sensors and six-step commutation for control until an initial hall transition occurs. Then they switch to using the incremental encoders for smoother commutation until the encoder index pulse is observed (once per motor revolution).

  • Page 76: Appendix Dglossary

    However, for a fixed position and orientation of the tool frame the arm pose is fixed. When there are more degrees of freedom than 6-space, the robot arm kinematics are called redundant. For example, a seven-degree-of-freedom robotic arm such as the WAM arm remains free to move even while holding a position and orientation.
  • Page 77 WAM Arm – User’s Manual support@barrett.com www.barrett.com Denavit-Hartenberg Parameters - The D-H parameters form an n x 4 matrix of parameters that define the kinematic relationship between coordinate frames that are attached to links in a robot. Knowledge of the D-H parameters allows immediate construction of the transformation matrices.
  • Page 78 Puck™ - An ultra-miniature brushless servo controller fit into an ultra-high-precision encoder. Developed over several years by Barrett Technology, this puck weighs only 44gms and is only 35mm (dia) x 17 (high) with connectors. The Puck™ fulfills both definitions of a Controller (see Controller).

  • Page 79: Index

    WAM Arm – User’s Manual support@barrett.com www.barrett.com Index Haptic Objects ........77 Home Position ........27, 77 Backdrivable ........71, 76 Backdrivable Robot........76 BarrettHand™ ........70, 76 Jacobian............ 77 Inverse ..........78 Transpose..........78 Cables (mechanical tension elements) 26, 76 Differential ........7, 74 Micro-Yielding........78...
  • Page 80 WAM Arm – User’s Manual support@barrett.com www.barrett.com Support Reference Sheet ......16 Trajectories ........53, 54 Support Subscription ........ 16 Updates ..........52 Troubleshooting:........52 Troubleshooting Cables ........... 53 Voltage.......... 10, 56, 71 Gravity Compensation......53 Joints..........51, 53, 54 Pendants .........54, 55 WAM™...

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