Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J9/00—Programme-controlled manipulators
  • B25J9/10—Programme-controlled manipulators characterised by positioning means for manipulator elements
  • B25J9/106—Programme-controlled manipulators characterised by positioning means for manipulator elements with articulated links
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J9/00—Programme-controlled manipulators
  • B25J9/02—Programme-controlled manipulators characterised by movement of the arms, e.g. cartesian coordinate type
  • B25J9/04—Programme-controlled manipulators characterised by movement of the arms, e.g. cartesian coordinate type by rotating at least one arm, excluding the head movement itself, e.g. cylindrical coordinate type or polar coordinate type
  • B25J9/041—Cylindrical coordinate type
  • B25J9/042—Cylindrical coordinate type comprising an articulated arm

Definitions

• This invention relates to a robotic arm or manipulator.
• a robotic arm of the form comprising a shoulder section, a first arm section connected to the shoulder section for rotation about a first pivot axis, a second arm section connected to the first arm section for rotation
• the invention has for its aim to provide a robotic arm of the construction set out above which enables accurate control of a device, e * g. a gripper carried.by the output member, while permitting a wide range of movement of the device, simple control of the drive means and economic manufacture.
• a robotic arm according to the invention is characterised in that the drive means includes first drive means for rotating the first arm section about the first axis, second drive means for rotating the second arm about the second axis, and third drive means for rotating the output member about the third axis, the first, second and third drive means being operable independently of each other and being so arranged that the output member can be driven radially of the first axis by operation of the first and second drive means at equal speeds, and operation of the second drive means causes also the output member to be rotated about the third axis through an angle equal to half the angle through which the second arm section is rotated about the second axis.
• the arm of the invention can be used to advantage in conjunction with the robotic wrist and gripper assembly described in International Patent Application No.
• PCT/GB86/00123 which will be mounted on the output member of the arm, and with the linear guideway and carriage assembly described in International Patent Application No. PCT/GB86/001*_8, the shoulder section of the arm * being fastened to the carriage for vertical adjustment of the arm.
• the arm especially when in combination with these assemblies, is suitable for use either on a mobile robot or mounted on a stationary base.
• the first, second and third drive means comprise respect ⁇ ive electric motors, the first motor being carried by the shoulder section and the second and third motors being carried by the first arm section.
• Each motor drives a pulley through a gearbox and a system of belts and pulleys providing further gear reduction.
• the latter system enables standard gearboxes to be used by reducing backlash, e.g. from about 2 for such a gearbox to about 0.05°, whereby costs are kept down but accurate control is still possible to within less than one millimetre.
• Figure 1 is a section through a robotic arm embodying the invention
• Figure 2 is an end view of the arm
• Figure 3 s a plan view of the first arm section, some parts having been omitted in the interest of clarity;
• Figures k and 5 are schematic plan views of the arm illustrating operation thereof.
• the robotic arm illustrated in detail in Figures 1 - 3 ⁇ comprises a shoulder section 1 adapted to be mounted on a carriage for vertical movement of the arm, a first or upper arm section 2 connected to the section 1 for rotation about a vertical axis A, a second or lower arm section 3 connected to the upper section 2 for rotation about a vertical axis B, and an " output member journalled in the lower arm section 3 for rotation about a vertical axis C, the length of the upper arm 2 between the axes A and B being equal to the length of the lower arm 3 between the axes B and C.
• the shoulder section 1 includes a support frame 10 including a horizontal platform 11 in which is fixed the upper end of a vertical tubular spindle 12 defining axis A. Also mounted on the platform 11 are a first electric drive motor l with its encoder 15 and gear ⁇ box l6, and an eccentric spindle 17 carrying freely rotatable combined pulleys 18, 19- One toothed belt 21 is trained around the pulley 18 and a drive pulley 22 provided on the output shaft of the gearbox 16. A second toothed belt 23 is trained around pulley 19 and a driven pulley 2k journalled on the spindle 12.
• the spindle 17 is normally held fixed in the boss 25 on platform 11 by a clamping screw 26, but after loosen- ing this screw the eccentric spindle can be rotated for adjusting the tension in belt 23-
• a mounting plate supporting motor l4 has slots through which screws 13 pass so that by moving the motor the distance between pulleys 18 and 20 can be varied to obtain the required tension in the belt
• the lower end of spindle 12 is supported by a second platform 27 of the support frame 10, " and the upper arm 2 comprises a moulding 28 journalled on the spindle 12 between the platforms 11, 27 by bearings 29.
• the driven pulley 2k is fixed to the moulding 28 by screws 30 so that energising the motor lk causes the upper arm 2 to be rotated about axis A.
• the rotation of upper arm 2 is limited e.g. to l8 ⁇ ° by a semi-circular groove 31 formed in the bottom of moulding 28 and in which engages a stop pin 32 fixed to platform 27 *
• a vertical tubular spindle 35 defining axis B is journalled in the moulding 28 at the end remote from spindle 12 by bearings 36 and has a driven pulley 37 fast with its upper end.
• a second electric motor 38 for driving pulley 37 a second electric motor 38 together with its encoder 39.
• gearbox kO and mounting plate kl are carried on the moulding and fixed by screws k2.
• Combined pulleys 43» kk are freely rotatable on an eccentric spindle 45 fixed by a clamping screw 46 in a boss of moulding 28, a first toothed belt 7 being trained around pulley 43 and a driving pulley 49 fitted to the output shaft of the gearbox 40, and a second toothed belt 48 being trained around pulleys 44 and 37 *
• the tension in belts 47, 48 is adjustable in the same way as belts 21, 23 » that is the eccentric spindle 45 being rotatable after releasing the clamp screw 46 to adjust the tension in belt 48, and the mounting plate 4l for the motor 38 having slots for the screws 42 to allow the motor to be moved to adjust the tension in belt 47•
• the lower arm 3 is formed by a moulding 50 -and is fixed to the lower end of spindle 35 by grubscrews 51 provided in a sleeve 52 fitted in the moulding 50.
• energising motor 38 through the gearbox 4 ⁇ and system of pulleys and belts causes the spindle 35 and hence the lower arm 3 to be rotated about axis B.
• the gear ratio between motor 38 and spindle 35 is twice that between motor 14 and the pulley 24, this breing conveniently achieved by the pulleys 49, 43, 44 being the same as pulleys 22, l8, 19 respectively, and pulley 35 having half the number of teeth of the pulley 24.
• this arrangement allows the output member 4 to be driven in a direction radial to axis A by energising the motors 14, 38 to run at equal speeds in opposite directions.
• simple summation and subtraction, of position counts from the motor encoders can d fine arm motion in polar coordinates easily, with the minimum of software overhead.
• Rotation of the lower arm 3 is limited to an angle of about 330 by a stop finger 56 fixed to the upper arm abutting a stop formed by a web 57 of the moulding 50.
• the finger 5 can be fitted in either of the two positions shown in Figure 3 ⁇ enabling the lower arm to be turned either clockwise or counter clockwise about axis B to a position directly below upper arm 2, as shown in dashed line in Figure 1.
• This position of the lower arm is convenient for stowage and by allowing the lower arm to be turned selectively in either direction to that position is of advantage where a pair of arms are to be .mounted on either side of a mobile robot.
• the output member 4 consists of a plate 60 carried on a spindle 6l journalled by bearings 62 in the moulding 50 for rotation about axis C. Fast with the spindle is a pulley 63. For driving the pulley 63 a third electric motor 64 is provided and is carried by the upper arm 2. The motor 64, " its encoder 6 and gearbox 66 are supported on a mounting plate 67 fastened to the moulding 28 by screws 68.
• Combined pulleys 69, 70 are freely rotatable on the spindle 35 » and one toothed belt 72 is trained around a drive pulley 71 fitted to the output shaft of the gearbox 66 and pulley 69, and another toothed belt 73 is trained around pulleys 63 and 70.
• the ratio of the numbers of teeth of the pulleys 63 and 70 is 2:1, which means that if motor 64 remains stationary and motor 38 is energised, the output member 4 will be rotated about "axis C through an angle which is half that through which the lower arm is rotated about axis B. As a consequence the orientation of a wrist and gripper carried by member 4, will remain fixed with respect to the direction A-C, as explained below.
• the rotati'on of. the output member about axis C is limited e.g. to l8 ⁇ ° by a stop 75 on the plate 60 engaging in a semi-circular groove in the underside of the mould- ing 50.
• the position and orientation of a device, in particular a wrist and gripper, carried by the output member 4 are widely variable within the horizontal plane.
• the use of the two stage pulley and belt transmissions to provide gear reduction enables the use of standard gearboxes 16, 40 , 66 whereby manufacturing costs are kept down without forfeiture of accurate control.

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• Engineering & Computer Science (AREA)
• Robotics (AREA)
• Mechanical Engineering (AREA)
• Manipulator (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10579054

Family Applications (1)

Country Status (4)

Cited By (8)

Citations (12)

• 1985
  • 1985-05-13 GB GB858512056A patent/GB8512056D0/en active Pending
• 1986
  • 1986-05-13 AU AU58154/86A patent/AU5815486A/en not_active Abandoned
  • 1986-05-13 WO PCT/GB1986/000262 patent/WO1986006673A1/en unknown
  • 1986-05-13 JP JP50285086A patent/JPS62502844A/ja active Pending

Patent Citations (12)

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