Power-assisted cart

• US 5,746,282 A
• Filed: 04/12/1996
• Issued: 05/05/1998
• Est. Priority Date: 04/14/1995
• Status: Expired due to Term

• Current Assignee: Panasonic Healthcare Holdings Co., Ltd.
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Maeda, Hiroshi, Fujiwara, Shigeki, Yamashita, Hideki
• Primary Examiner(s): AVILA, STEPHEN P
• Application Number:
  US08/629,945
• Time in Patent Office: 753 Days
• Field of Search: 180/6.2, 180/6.28, 180/6.44, 180/6.48, 180/6.5, 180/6.26, 180/6.24, 180/7.1, 180/19.1, 180/19.2, 180/19.3, 180/3.5, 180/170
• US Class Current: 180/6.2
• CPC Class Codes: B60K 26/02 of initiating means or elements
• CPC Class Codes: B60L 15/00 Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2200/44 Industrial trucks or floor conveyors
• CPC Class Codes: B60L 2220/46 Wheel motors, i.e. motor connected to only one wheel
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/24 Steering angle
• CPC Class Codes: B60L 50/53 in combination with an external power supply, e.g. from overhead contact lines
• CPC Class Codes: B62B 3/1476 the main load support being a platform
• CPC Class Codes: B62B 5/0026 Propulsion aids
• CPC Class Codes: B62B 5/0073 Measuring a force
• CPC Class Codes: B62B 5/06 Hand moving equipment, e.g. handle bars for cycles B62K11/14, B62K21/12
• CPC Class Codes: B62D 51/04 the driver walking
• CPC Class Codes: Y02P 90/60 Electric or hybrid propulsion means for production processes
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A power-assisted cart includes a wheeled platform for supporting a load thereon; driving wheels mounted on the wheeled platform for, when driven, moving the wheeled platform; a drive unit for driving the driving wheels; an operating unit which may be in the form of a handle mounted on the wheeled platform for receiving an external force applied thereto when the cart is desired to be moved; a force detector for detecting a magnitude and direction of the external force applied to the operating unit; and a control for generating to the drive unit an output substantially proportional to the external force detected by the force detector.

Claims

1. A power-assisted cart comprising:

a wheeled platform for supporting a load thereon;

a first driving wheel mounted on the wheeled platform for, when driven, moving the wheeled platform;

a drive means for driving the first driving wheel;

an operating member mounted on the wheeled platform for receiving an external force applied thereto when the cart is desired to be moved;

a force detector for detecting a magnitude and direction of the external force applied to the operating member to thereby detect thrust and yawing forces applied to the power-assisted cart; and

a control means for controlling the drive means to apply a torque to the first driving wheel substantially proportional to the external force detected by the force detector so that the external force, when added to a force resulting from the torque applied to the first driving wheel results in a desired total force being applied to the cart.

2. The power-assisted cart as claimed in claim 1, further comprising a change detector for detecting a rate of change of the external force applied to the operating member, and wherein said control means is operable to correct the torque based on the change rate detected by the change detecting means.

3. The power-assisted cart as claimed in claim 1, wherein the control means includes a force sensor for detecting a first range of values of the external force applied to the operating member and, wherein the control means is operable to correct the torque based on the values so detected, and wherein the first range of values include values of the external force which have a magnitude below a threshold level.

4. The power-assisted cart as claimed in claim 1, further comprising speed detecting means for detecting a traveling speed of the power-assisted cart, wherein the control means corrects the torque based on the traveling speed detected by the speed detecting means.

5. The power-assisted cart as claimed in claim 4, wherein the control means is operable to suspend application of torque when the traveling speed detected by the speed detecting means exceeds a predetermined value.

6. The power-assisted cart as claimed in claim 4, wherein the control means utilizes an amplification factor to calculate a desired amount of torque based on the detected external force, wherein, when the torque generated by the drive means is increasing with an increase of the traveling speed detected by the speed detecting means, the control means decreases the amplification factor.

8. The power-assisted cart as claimed in claim 4, wherein the control means includes a resistance adding means for increasing the torque based on a rolling resistance.

9. The power-assisted cart as claimed in claim 4, wherein the control means includes a static friction adding means for increasing the torque based on a static frictional resistance.

10. A power-assisted cart in claim 4, comprising:

a wheeled platform for supporting a load thereon;

a first driving wheel mounted on the wheeled platform for, when driven, moving the wheeled platform;

a drive means for driving the first driving wheel;

an operating member mounted on the wheeled platform for receiving an external force applied thereto when the cart is desired to be moved;

speed detecting means for detecting a traveling speed of the power-assisted cart, wherein the control means corrects the torque based on the traveling speed detected by the speed detecting means;

inclination detecting means for detecting an inclination of the cart, and wherein the control means corrects the torque based on the inclination detected by the inclination detecting means;

a force detector for detecting a magnitude and direction of the external force applied to the operating member to thereby detect thrust and yawing forces applied to the power-assisted cart; and

a control means for controlling the drive means to apply a torque to the first driving wheel substantially proportional to the external force detected by the force detector.

11. The power-assisted cart as claimed in claim 4, further comprising a second driving wheel, wherein the first and second driving wheels are independently driven by the driving means, and wherein the first driving wheel is mounted on a left portion of the wheeled platform and the second driving wheel is mounted on a right portion of the wheeled platform, and wherein the speed detecting means detects the speed of each of the first and second driving wheels and the control means independently controls each of the first and second driving wheels.

12. The power-assisted cart as claimed in claim 11, wherein the control means is operable to increase a difference between rotational speeds of the first and second driving wheels when a difference between the rotational speeds of the first and second driving wheels is small as compared to a detected value of the yawing force.

13. The power-assisted cart as claimed in claim 11, wherein the control means is operable to decrease a difference between the torque applied to the first driving wheel and the torque applied to the second driving wheel when a difference in rotational speed between the first and second driving wheels is large as compared with a detected value of the yawing force.

14. The power-assisted cart as claimed in claim 1, further comprising a load detecting means, wherein the control means corrects the torque based on a load value detected by said load detecting means.

15. The power-assisted cart as claimed in claim 14, wherein the load detecting means includes a load sensor for detecting whether a load is present on the wheeled platform.

16. The power-assisted cart as claimed in claim 14, wherein the load detecting means includes a weight sensor for detecting a weight of a load on the wheeled platform.

20. The power-assisted cart as claimed in claim 1, further comprising a second driving wheel, wherein the first and second driving wheels are independently driven by the driving means and wherein the first driving wheel is mounted on a left portion of the wheeled platform and the second driving wheel is mounted on a right portion of the wheeled platform, and wherein a first amount of torque corresponding to the external force acting in a direction parallel to a direction of travel of the cart and a second amount of torque corresponding to an external force acting in a steering direction are applied to each of the first and second driving wheels to achieve the desired total force.

21. The power-assisted cart as claimed in claim 20, further comprising front and rear casters mounted on the wheeled platform at respective locations conforming to the direction of travel of the power-assisted cart, and wherein said driving wheels are positioned on respective left and right sides of the cart and intermediate of the length of the wheeled platform.

22. The power-assisted cart as claimed in claim 1, further comprising a clutch disposed between the drive means and the first driving wheel.

7. A power-assisted cart comprising:

a wheeled platform for supporting a load thereon;

a first driving wheel mounted on the wheeled platform for, when driven, moving the wheeled platform;

a drive means for driving the first driving wheel;

an operating member mounted on the wheeled platform for receiving an external force applied thereto when the cart is desired to be moved;

speed detecting means for detecting a traveling speed of the power-assisted cart, wherein the control means corrects the torque based on the traveling speed deteted by the speed detecting means;

a force detector for detecting a magnitude and direction of the external force applied to the operating member to thereby detect thrust and yawing forces applied to the power-assisted cart; and

a control means for controlling the drive means to apply a torque to the first driving wheel substantially proportional to the external force detected by the force detector, wherein the control means includes a viscosity adding means for decreasing the torque by applying a viscous resistance to the drive means, wherein the viscous resistance is substantially proportional to the traveling speed detected by the speed detecting means.

17. A power-assisted cart comprising:

a wheeled platform for supporting a load thereon;

a first driving wheel mounted on the wheeled platform for, when driven, moving the wheeled platform;

a drive means for driving the first driving wheel;

an operating member mounted on the wheeled platform for receiving an external force applied thereto when the cart is desired to be moved;

speed detecting means for detecting a traveling speed of the power-assisted cart, wherein the control means corrects the torque based on the traveling speed detected by the speed detecting means;

load detecting means, wherein the control means corrects the torque based on a load value detected by said load detecting means, wherein the load detecting means includes a weight sensor for detecting a weight of a load on the wheeled platform;

a force detector for detecting a magnitude and direction of the external force applied to the operating member to thereby detect thrust and yawing forces applied to the power-assisted cart; and

a control means for controlling the drive means to apply a torque to the first driving wheel substantially proportional to the external force detected by the force detector, wherein the control means includes a frictional resistance adding means for increasing the torque based on the weight detected by the weight sensor.

18. A power-assisted cart comprising:

a wheeled platform for supporting a load thereon;

a first driving wheel mounted on the wheeled platform for, when driven, moving the wheeled platform;

a drive means for driving the first driving wheel;

an operating member mounted on the wheeled platform for receiving an external force applied thereto when the cart is desired to be moved;

speed detecting means for detecting a traveling speed of the power-assisted cart, wherein the control means corrects the torque based on the traveling speed detected by the speed detecting means;

inclination detecting means for detecting an inclination of the power-assisted cart;

a force detector for detecting a magnitude and direction of the external force applied to the operating member to thereby detect thrust and yawing forces applied to the power-assisted cart; and

a control means for controlling the drive means to apply a torque to the first driving wheel substantially proportional to the external force detected by the force detector, wherein the control means corrects the torque based on the detected inclination.

19. The power-assisted cart as claimed in claim 18, wherein the control means is operable to correct the torque based on the inclination detected by the inclination detecting means by applying an additional force component to the cart, wherein the additional force component is selected to counterbalance an incline force to achieve the desired total force, wherein the incline force tends to cause the cart to descend the inclination.