STEERING SYSTEM FOR HEAVY MOBILE MEDICAL EQUIPMENT

Abstract

In one embodiment of the invention, a steering system for mobile medical equipment is disclosed including left and right steerable wheel assemblies including left and right steerable wheels, left and right parallelogram linkages coupled to the left and right steerable wheel assemblies, a steering function generator coupled to the left and right parallelogram linkages, and a steering tiller coupled to the steering function generator. The left and right parallelogram linkages transfer differing left and right wheel angles to the left and right steerable wheel assemblies respectively. The steering function generator generates the left wheel angle (LWA) of the left steerable wheel and the right wheel angle (RWA) of the right steerable wheel. The steering tiller receives an input steering angle to generate the left wheel angle and the right wheel angle to control the direction of the mobile medical equipment around flooring.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1A is a block diagram of a robotic surgery system to perform minimally invasive robotic surgical procedures using one or more robotic surgical arms.

FIG. 1B is a perspective view of the robotic patient-side system of FIG. 1A with the one or more robotic surgical arms coupled thereto.

FIG. 2A is a perspective side view of a mobile base for the robotic patient side system of FIG. 1B.

FIG. 2B is a bottom view of the mobile base illustrated in FIG. 2A.

FIG. 3 is a diagram illustrating a top view of the mobile base with lines of axes through axels of the wheels of the mobile base.

FIGS. 4A-4E are series of diagrams illustrating the desired steering linkage behavior for right turns of the mobile base and patient side cart.

FIG. 5 is a diagram illustrating the desired steering linkage behavior for a zero radius turn of the mobile base and patient side cart.

FIG. 6 is a graph of the tiller angle TA versus the left wheel angle LWA and the right wheel angle RWA of the steerable wheels of the mobile base.

FIG. 7 is a perspective cutaway view of the mobile base to illustrate the steering system of the patient side cart.

FIG. 8 illustrates a top cutaway view of the mobile base without the steering tiller subassembly to better illustrate subassemblies of the steering system of the patient side cart.

FIG. 9 illustrates a perspective side view of a steering tiller subassembly removed from the mobile base.

FIG. 10 illustrates a perspective side view of a function generator subassembly removed from the mobile base.

FIG. 11 illustrates a perspective side view of parallelogram linkage removed from the mobile base.

FIG. 12 illustrates a perspective side view of a wheel assembly removed from the mobile base.

FIG. 13 illustrates a top view of a portion of the steering system mounted in the mobile base of the patient side cart.

FIG. 14 illustrates a side perspective view of a short link for the steering system of the mobile base and patient side cart.

FIG. 15 illustrates a bottom side perspective view of a portion of the steering system mounted in the mobile base of the patient side cart.

FIG. 16 illustrates a top view of the steering system mounted in the mobile base of the patient side cart.

FIGS. 17A-17C illustrate the movement of the steering system and its linkage as it moves to steer left and right from center.

FIGS. 18A-18C illustrate schematic diagrams of the steering linkage in different positions.

Claims

1. A mobile medical equipment system comprising: a mobile base to movably support medical equipment, the mobile base including a chassis having a left side, a right side, a front side, and a back side;at least one non-steerable wheel rotatably coupled to the chassis near the front side, the at least one non-steerable wheel to roll the mobile medical equipment system over a floor;a first steerable wheel and a second steerable wheel spaced apart and pivotally coupled to the chassis near the back side, the first and second steerable wheels to steer the mobile medical equipment system around the floor; anda steering system coupled to the chassis and the first and second steerable wheels, the steering system to receive directional input from a user, the steering system having a steering angle function generator to couple the directional input to the first and second steerable wheels.

2. The mobile medical equipment system of claim 1, wherein the steering angle function generator includes a pair of cam followers in a pair of cam follower slots to couple the directional input to the first and second steerable wheels.

3. The mobile medical equipment system of claim 1, wherein the medical equipment is a robotic surgical system including one or more robotic surgical arms.

4. The mobile medical equipment system of claim 1, wherein the steering angle function generator unequally converts the directional input from the user to the first and second steerable wheels such that a first wheel angle of the first steerable wheel does not equal a second wheel angle of the second steerable wheel unless the mobile medical equipment is to move straight ahead.

5. The mobile medical equipment system of claim 1, wherein a tiller is rotatably coupled to the chassis near the back side to receive the directional input from the user.

6. The mobile medical equipment system of claim 5, wherein the steering angle function generator includes a pair of cam plates having a pair of cam follower slots,a pair of short links having a pair of cam followers inserted into the pair of cam follower slots in the cam plates,a long link coupled between the pair of short links,a tiller link coupled to the long link and the tiller; andthe steering system further has a first parallelogram linkage coupled between a first cam plate of the pair of cam plates and the first steerable wheel, anda second parallelogram linkage coupled between a second cam plate of the pair of cam plates and the second steerable wheel.

7. The mobile medical equipment system of claim 6, wherein the first parallelogram linkage includes a first caster link coupled to a caster of the first steerable wheel,a first front steering link coupled between the first cam plate and the first caster link, anda first rear steering link spaced apart from the first front steering link and coupled between the first cam plate and the first caster link,and the second parallelogram linkage includes a second caster link coupled to a caster of the second steerable wheel,a second front steering link coupled between the second cam plate and the second caster link, anda second rear steering link spaced apart from the second front steering link and coupled between the second cam plate and the second caster link.

8. The mobile medical equipment system of claim 1, wherein the steering system includes a pair of angled arms having the pair of cam follower slots, a first angled arm of the pair of angled arms coupled to the first steerable wheel and a second angled arm of the pair of angled arms coupled to the first steerable wheel,a sliding bar having the pair of cam followers inserted into the pair of cam follower slots of the pair of angled arms, the sliding bar having a third cam follower,a tiller link having a cam follower slot over the third cam follower in the sliding bar.

9. The mobile medical equipment system of claim 2, wherein widths of the cam follower slots are larger than a diameter of the cam followers to reduce wear in the steering system.

10. The mobile medical equipment system of claim 1, wherein the at least one non-steerable wheel is a motorized wheel to drive the mobile medical equipment over the floor.

11. A method for steering mobile medical equipment having four wheels, the method comprising: generating a left wheel angle and a right wheel angle in response to an input steering angle other than zero, the right wheel angle differing from the left wheel angle;transferring the left wheel angle to a left wheel assembly to position a left steerable wheel;transferring the right wheel angle to a right wheel assembly to position a right steerable wheel; andwherein the position of the right steerable wheel differs from the position of the left steerable wheel such that the axis of rotation of a pair of front wheels substantially intersects different axes of rotation of the right steerable wheel and the left steerable wheel at a center of turn to turn the mobile medical equipment over a floor substantially around the center of turn.

12. The method of claim 11, further comprising receiving the input steering angle.

13. The method of claim 12, further comprising driving a pair of motorized wheels to move the mobile medical equipment over the floor.

14. The method of claim 11, further comprising limiting the generating of the left wheel angle and the right wheel angle to avoid radius turns of substantially zero degrees.

15. The method of claim 14, wherein the limiting of the generating of the left wheel angle and the right wheel angle includes keeping the right steerable wheel and the left steerable wheel from pointing in opposite directions, wherein left and right are opposite directions.

16. The method of claim 15, wherein the limiting of the generating of the left wheel angle and the right wheel angle includes keeping the right steerable wheel and the left steerable wheel pointing towards a similar direction.

17. The method of claim 16, wherein the similar direction is left and the right steerable wheel and the left steerable wheel are kept pointing towards the left to avoid radius turns of substantially zero degrees.

18. The method of claim 16, wherein the similar direction is right and the right steerable wheel and the left steerable wheel are kept pointing towards the right to avoid radius turns of substantially zero degrees.

19. A steering system for mobile medical equipment comprising: a left steerable wheel assembly including a left steerable wheel;a right steerable wheel assembly including a right steerable wheel;a left parallelogram linkage coupled to the left steerable wheel assembly, the left parallelogram linkage to transfer a left wheel angle to the left steerable wheel assembly;a right parallelogram linkage coupled to the right steerable wheel assembly, the right parallelogram linkage to transfer a right wheel angle to the right steerable wheel assembly;a steering function generator coupled to the left parallelogram linkage and the right parallelogram linkage, the steering function generator to generate the left wheel angle (LWA) of the left steerable wheel and the right wheel angle (RWA) of the right steerable wheel; anda steering tiller coupled to the steering function generator, the steering tiller to receive an input steering angle from an operator to generate the left wheel angle and the right wheel angle to control the direction of the mobile medical equipment around flooring.

20. The steering system of claim 19, wherein the steering function generator includes a left cam follower and a right cam follower; andeach of the left parallelogram linkage and the right parallelogram linkage include a cam plate having a cam follower slot to receive a cam follower to generate a wheel angle,a caster link coupled to the steerable wheel assembly, the caster link to couple the wheel angle to the steerable wheel,a front steering link coupled between a first end of the cam plate and a first end of the caster link, anda rear steering link spaced coupled between a second end of the cam plate opposite the first and a second end of the caster link opposite the first,wherein the front steering link and the rear steering link transfer the wheel angle from the cam plate to the caster link.

21. The steering system of claim 20, wherein the cam follower slot in the cam plate is linear to provide a linear cam profile to generate the wheel angle.

22. The steering system of claim 20, wherein the cam follower slot in the cam plate is curved to provide a curved cam profile to generate the wheel angle.

23. The steering system of claim 20, wherein the cam follower slot in the cam plate is complex to provide a complex cam profile to generate the wheel angle.

24. The steering system of claim 20, wherein a width of the cam follower slot is larger than a diameter of the cam follower to reduce wear in the steering system.

25. The steering system of claim 19, wherein the steering function generator includes a tiller link coupled to the steering tiller, the tiller link pivotally coupled to a chassis near a first end, the tiller link to receive the input steering angle from the steering tiller and pivot about the first end,a long link pivotally coupled to the tiller link between a first end and a second end opposite the first end, the long link to convert the pivotal motion of the tiller link to a linear sweeping motion,a left short link having a first end pivotally coupled to the chassis, the left short link pivotally coupled near a first end of the long link between the first end and a second end of the left short link, the left short link to convert the linear sweeping motion of the long link into pivotal motion and couple it to the left parallelogram linkage, anda right short link having a first end pivotally coupled to the chassis, the right short link pivotally coupled near a second end of the long link between the first end and a second end of the right short link, the right short link to convert the linear sweeping motion of the long link into pivotal motion of the right short link and couple it to the right parallelogram linkage.

26. The steering system of claim 25, wherein the steering tiller includes a pinion gear andthe tiller link of the steering function generator includes an arctuate gear segment meshed to the pinion gear to receive the input steering angle.

27. The steering system of claim 19, wherein the left parallelogram linkage to further transfer a torque from the steering function generator to the left steerable wheel maintaining a mechanical advantage over a range of motions to ease the steering of the mobile medical equipment; andthe right parallelogram linkage to further transfer a torque from the steering function generator to the right steerable wheel maintaining a mechanical advantage over a range of motions to ease the steering of the mobile medical equipment.

28. A method for steering mobile medical equipment having four wheels, the method comprising: receiving an input steering angle other than zero and generating a pivotal motion in a first link;converting the pivotal motion of the first link into a linear sweeping motion of a second link;converting the linear sweeping motion of the second link into a pivotal motion of a third link and a fourth link, the fourth link spaced apart from the third link;unequally transferring the pivotal motion of the third link and the fourth link respectively into a first parallelogram linkage and a second parallelogram linkage;transferring the pivotal motion in the first parallelogram linkage to a first wheel assembly to form a first wheel angle; andtransferring the pivotal motion in the second parallelogram linkage to a second wheel assembly to form a second wheel angle,wherein the first wheel angle differs from the second wheel angle in response to the unequal transfer of the pivotal motion.

29. The method of claim 28, wherein the transferring of the pivotal motion in the first parallelogram linkage to the first wheel assembly includes laterally moving a first front steering link a first distance in a first direction, andlaterally moving a first rear steering link a second distance in a second direction opposite to the first direction, andpivoting a first caster link coupled to the first wheel assembly in response to the lateral movement of the first front steering link and the first rear steering link; andthe transferring of the pivotal motion in the second parallelogram linkage to the second wheel assembly includes laterally moving a second front steering link a third distance in the first direction, andlaterally moving a second rear steering link a fourth distance in the second direction opposite to the first direction, andpivoting a second caster link coupled to the second wheel assembly in response to the lateral movement of the second front steering link and the second rear steering link,wherein the third distance differs from the first distance and the fourth distance differs from the second distance.

30. The method of claim 29, wherein the unequal transfer of the pivotal motion into the first parallelogram linkage and the second parallelogram linkage includes respectively sliding a first cam follower in a first cam follower slot and sliding a second cam follower in a second cam follower slot.

31. The method of claim 29, further comprising: maintaining a mechanical advantage in the first parallelogram linkage and the second parallelogram linkage over a wide range of motion to efficiently transfer a torque from a tiller to the first wheel assembly and the second wheel assembly, respectively, and ease the steering of the mobile medical equipment.