Powered caster wheel module for use on omnidirectional drive systems

• US 6,491,127 B1
• Filed: 08/14/1998
• Issued: 12/10/2002
• Est. Priority Date: 08/14/1998
• Status: Expired due to Fees

• Current Assignee: Nomadic Technologies
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Holmberg, Robert, Slater, James C.
• Primary Examiner(s): Mai, Lanna
• Assistant Examiner(s): Ilan, Ruth
• Application Number:
  US09/134,241
• Time in Patent Office: 1,579 Days
• Field of Search: 180/234, 180/236, 180/23, 180/24.08, 180/211, 180/212, 180/15, 180/16, 180/12, 180/13, 180/65.1, 180/65.5, 180/65.6, 180/252, 180/253, 180/24.06, 180/24.07, 180/21, 901/1, 301/5.3, 301/6.5
• US Class Current: 180/252
• CPC Class Codes: B60K 17/043 Transmission unit disposed in on near the vehicle wheel, or between the differential gear unit and the wheel
• CPC Class Codes: B60K 17/30 the ultimate propulsive elements, e.g. ground wheels, being steerable
• CPC Class Codes: B60K 17/303 with a gearwheel on the steering knuckle or kingpin axis
• CPC Class Codes: B60K 2007/0046 the motor moving together with the vehicle body, i.e. moving independently from the wheel axle
• CPC Class Codes: B60K 2007/0084 the motor axle being vertical
• CPC Class Codes: B60K 7/0007 the motor being electric
• CPC Class Codes: B60L 2220/46 Wheel motors, i.e. motor connected to only one wheel
• CPC Class Codes: B62D 7/026 characterised by comprising more than one bogie, e.g. situated in more than one plane transversal to the longitudinal centre line of the vehicle

Abstract

A drive system base or platform, such as for a mobile robot, is disclosed having multiple caster wheels, each wheel having its own first motor for independent driving and its own second motor for independent steering. Each wheel is rotably and pivotably mounted in a separate wheel module, which includes both the driving and steering motors associated with the wheel. All of the wheel modules on the base are identical and interchangeable. The two motors of each module are mounted side by side in a vertical arrangement for compactness. Each wheel module includes a suspension for allowing each wheel to move vertically and independently relative to the base. The hub and tread of each wheel are each cast concentrically around a bevel drive gear in an offset manner to provide a wheel and bevel gear that turn more smoothly and precisely.

Claims

1. A powered caster wheel module for use on a drive system, the module comprising:

a wheel mounted for rotation about a horizontal axis and pivotably mounted for steering about a vertical axis;

a first motor for driving the wheel about the horizontal axis;

a second motor for driving the wheel about the vertical axis; and

a housing for mounting the wheel and the two motors and attaching to a drive system base,

wherein both the first and second motors have armature axes that are vertical and closely spaced to provide the module with a small footprint and compact design,

vertical travel means located on the housing for allowing the housing to move vertically a predetermined distance with respect to a drive system base; and

means for suspending the drive system base from a housing such that a base can move along the vertical travel means with respect to the housing when the wheel travels over an uneven surface.

2. A drive system base comprising:

a drive system base member; and

a plurality of powered caster wheel modules, each module being substantially identical and including;

a wheel mounted for rotation about a horizontal axis and pivotably mounted for steering about a vertical axis;

a first motor mounted on the module for driving the wheel about the horizontal axis;

a second motor mounted on the module for driving the wheel about the vertical axis;

a housing for mounting the wheel and the two motors and attaching to the drive system base member;

vertical travel means located on the housing for allowing the housing to move vertically a predetermined distance with respect to the drive system base member; and

means for suspending the drive system base member relative to the housing such that the base member can move along the vertical travel means with respect to the housing when the wheel travels over an uneven surface, each of the wheels being able to move vertically independent of the other wheels;

wherein both the first and second motors have armature axes that are vertical and closely spaced to provide the module with a small footprint on the drive system base member and a compact design,

wherein each module is separately removable from the base member as an integral unit, and each module is freely interchangeable with one of the other modules.

3. A drive system base comprising:

a drive system base member; and

a plurality of powered caster wheel modules, each module being substantially identical and including;

a wheel mounted for rotation about a horizontal axis and pivotably mounted for steering about a vertical axis;

a first motor mounted on the module for driving the wheel about the horizontal axis;

a second motor mounted on the module for driving the wheel about the vertical axis; and

a housing for mounting the wheel and the two motors and attaching to the drive system base member,

wherein both the first and second motors have armature axes that are vertical and closely spaced to provide the module with a small footprint on the drive system base member and a compact design,

wherein each module is separately removable from the base member as an integral unit, and each module is freely interchangeable with one of the other modules,

wherein each of the wheels comprises;

a beveled gear having a central bore for accommodating at least one bearing to support the gear for rotational motion, the gear having a plurality of gear teeth disposed circumferentially around an axial end of the gear;

a rigid hub cast concentrically around the beveled gear and extending radially outward therefrom allowing the gear teeth to protrude from an axial side of the hub; and

a resilient tread with an outer periphery cast concentrically around an outer circumference of the hub such that the outer periphery of the tread is precisely aligned concentrically with the central bore of the gear.

4. A drive system comprising:

a base member; and

a plurality of powered caster wheel modules, each module being substantially identical and including;

a wheel mounted for rotation about a horizontal axis and pivotably mounted for steering about a vertical axis, the wheel being mounted in a caster fashion such that the horizontal rotation axis and the vertical steering axis do not intersect, the wheel including a beveled gear having a central bore for accommodating at least one bearing to support the gear for rotational motion, the gear having a plurality of gear teeth disposed circumferentially around an axial end of the gear, the wheel including a rigid hub cast concentrically around the beveled gear and extending radially outward therefrom allowing the gear teeth to protrude from an axial side of the hub, and a resilient tread with an outer periphery cast concentrically around an outer circumference of the hub such that the outer periphery of the tread is precisely aligned concentrically with the central bore of the gear;

a first motor mounted on the module for driving the wheel about the horizontal axis;

a second motor mounted on the module for driving the wheel about the vertical axis; and

a housing for mounting the wheel and the two motors and attaching to the base member,

vertical travel means located on the housing for allowing the housing to move vertically a predetermined distance with respect to the base member; and

means for suspending the base member relative to the housing such that the base member can move along the vertical travel means with respect to the housing when the wheel travels over an uneven surface,

each of the wheels being able to move vertically independent of the other wheels,

wherein both the first and second motors of each module have armature axes that are vertical and closely spaced to provide the module with a small footprint on the base member and a compact design, and

wherein each module is separately removable from the base member as an integral unit, and each module is freely interchangeable with one of the other modules.

5. A drive system according to claim 4, wherein the drive system base member is supported above the ground entirely by the wheels of the substantially identical wheel modules.