System and method for managing a current flow in a lift machine

• US 9,422,141 B2
• Filed: 10/22/2010
• Issued: 08/23/2016
• Est. Priority Date: 10/22/2010
• Status: Active Grant

• Current Assignee: TLD Canada, Inc.
• Original Assignee: TLD Canada, Inc.
• Inventors: Foley, Martin
• Primary Examiner(s): SALATA, ANTHONY J
• Application Number:
  US13/880,766
• Publication Number:
  US 20130213744A1
• Time in Patent Office: 2,132 Days
• Field of Search: 187/203, 187/210, 187/211, 187/247, 187/277, 187/290, 187/293, 187/391, 187/393
• US Class Current: 1/1
• CPC Class Codes: B64F 1/32 for handling freight
• CPC Class Codes: B64F 1/322 Cargo loaders specially adapted for loading air freight containers or palletized cargo into or out of the aircraft
• CPC Class Codes: B66F 7/00 Lifting frames, e.g. for lifting vehicles; Platform lifts B66F11/04 takes precedence ; for lift-truck platform B66F9/06
• CPC Class Codes: B66F 7/0625 with wheels for moving around the floor
• CPC Class Codes: B66F 7/0633 Mechanical arrangements not covered by the following subgroups
• CPC Class Codes: B66F 7/065 Scissor linkages, i.e. X-configuration
• CPC Class Codes: B66F 7/08 hydraulically or pneumatically operated
• CPC Class Codes: B66F 9/24 Electrical devices or systems
• CPC Class Codes: H02J 15/003 in the form of hydraulic energy
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: Y02E 60/16 Mechanical energy storage, e.g. flywheels or pressurised fluids

Abstract

There is provided an energy management system for managing a current flow in a machine having a lift element being vertically movable by a motor assembly. The energy management system includes a power supplying bus for supplying the motor assembly, a battery source, an energy storage device and an associated controller, and a main controller for controlling the energy-storage-device controller and thus the powering of the motor assembly, while factoring a height and a movement of the lift element. The system generally seeks to manage the energy flow between the battery, motors and supercapacitors so as to maintain the battery current as low as possible by controlling the motor'"'"'s speed, to maintain the battery power demand constant over time, and to store the regenerated energy into supercapacitors in order to avoid recharging the battery during operation, as well as to maintain the supercapacitors energy level as high as possible.

Claims

1. An energy management system for managing a current flow in a machine having a lift element being vertically movable by a motor assembly, the energy management system comprising:

a power supplying bus for supplying the motor assembly;

a battery source being connected to the power supplying bus;

an energy storage device;

an energy-storage-device controller connected between the energy storage device and the power supplying bus, for controlling a current flow between the energy storage device and the power supplying bus;

sensors for detecting a height H and a movement of the lift element, said movement being selected from the group consisting of a lifting movement, a lowering movement and an immobile movement;

a first calculator connected to the sensors for calculating a minimum energy E_min required in the energy storage device as a function of the height H of the lift element;

a second calculator connected to the energy storage device for calculating an energy E_available stored in the energy storage device based on a voltage V_cap detected at terminals of the energy storage device and on a parameter of the energy storage device;

a comparator for calculating an Error where Error=E_min−

E_available;

a third calculator for setting a lower limit I_min of a current to be drawn from the energy storage device to 0 A when the movement detected by the sensors is the immobile or lowering movement, and for calculating the lower limit I_min as a function of Error when the movement detected by the sensors is the lifting movement;

a fourth calculator for calculating an upper limit I_max of a current to be supplied to the energy storage device as a function of Error when the movement detected by the sensors is the immobile or lowering movement; and

a main controller for controlling the energy-storage-device controller as a function of I_min, I_max, and the movement detected, to adjust the current flow between the energy storage device and the power supplying bus.

2. The energy management system according to claim 1, wherein the energy storage device comprises one or more supercapacitors.

3. The energy management system according to claim 1, wherein the energy-storage-device controller is a DC-DC converter.

4. The energy management system according to claim 1, wherein one of said sensors is an inclinometer for measuring an angle and for detecting the height H therefrom.

5. The energy management system according to claim 1, further comprising:

a memory storage unit for storing data; and

wherein said first, second, third and fourth calculators, said comparator and said main controller are provided in a Programmable Logic Controller being connected to the memory storage unit.

6. The energy management system according to claim 5, wherein one of said sensors is provided in the Programmable Logic Controller for detecting the movement of the lift element based on an operating command received at the Programmable Logic Controller.

7. The energy management system according to claim 1, in combination with said machine, the energy management system being operatively connected to the lift element.

8. The energy management system in combination with the machine according to claim 7, further comprising:

a supporting assembly for supporting the lift element; and

wherein one of said sensors is an inclinometer connected to the supporting assembly for measuring an angle and detecting the height H therefrom.

9. An energy management method for managing a current flow in a machine having a lift element being vertically operable by a motor assembly, the motor assembly being supplied with energy, through a power supplying bus, by a battery source and by an energy storage device via an energy-storage-device controller, the method comprising:

(a) detecting a height H and a movement of the lift element, said movement being selected from the group consisting of a lifting movement, a lowering movement and an immobile movement;

(b) calculating a minimum energy E_min required in the energy storage device as a function of the height H of the lift element;

(c) calculating an energy E_available stored in the energy storage device based on a voltage V_cap detected at terminals of the energy storage device and on a parameter of the energy storage device;

(d) calculating an error Error where Error=E_min−

E_available;

(e) setting a lower limit I_min of a current to be drawn from the energy storage device to OA when the movement detected at (a) is the immobile or lowering movement, and calculating the lower limit I_min as a function of Error when the movement detected at (a) is the lifting movement;

(f) calculating an upper limit I_max of a current to be supplied to the energy storage device as a function of Error when the movement is the immobile or lowering movement; and

(g) controlling the energy-storage-device controller as a function of I_min, I_max and the movement detected at (a) to manage the current flow between the energy storage device and the power supplying bus.

10. The method according to claim 9, wherein the determining at (a) comprises:

measuring an angle via an inclinometer; and

determining a height H of the platform as a function of the angle measured by the inclinometer.

11. The method according to claim 10, wherein the height is determined at (a) by means of a table of correspondence.

12. The method according to claim 9, further comprising:

providing an energy Ecap_n available in the energy storage device at n Volts, a maximum energy E_total which is storable in the energy storage device and maximum height H_total of the lifting element; and

wherein E_min is calculated at (c) according to;

E_min=Ecap_n+(E_total−

Ecap_n)/(H_total)×

H,

wherein

n is a constant having a value based on a parameter of the energy-storage-device controller and a voltage of the battery.

13. The method according to claim 12, wherein n=40V, Ecap_n=80,000 J, E_total=320,000 J and H_total=3,000 mm.

14. The method according to claim 9, wherein the parameter of the energy storage device is a Capacity provided in Farads and wherein the E_available is calculated at (c) according to:

E_available=(Capacity×

V_cap×

V_cap)/2.

15. The method according to claim 9, further comprising:

detecting a power state of the machine, said power state being selected from the group consisting of a powered state and a shutdown state; and

at (f), setting the lower limit I_min of said current to be drawn from the energy storage device to −

150 A when the power state detected is a shutdown state.

16. The method according to claim 9, further comprising:

detecting a voltage V_bat at terminals of the battery source; and

wherein, when the movement detected at (a) is the lifting movement, I_min is calculated at (f) according to;

if Error<

0 and Error>

−

2 then

I_min=Error×

75×

V_cap/V_bat

otherwise, if Error<

=−

2

I_min=−

150×

V_cap/V_bat

otherwise,

I_min=0,

17. The method according to claim 9, further comprising:

detecting a voltage V_bat at terminals of the battery source; and

wherein I_max is calculated at (g) according to;

if Error>

0 and Error<

2 then

I_max=Error×

75×

V_cap/V_bat

otherwise, if Error>

=2

I_max=150×

V_cap/V_bat

otherwise,

I_max=0.

18. The method according to claim 9, further comprising prior to (a):

calculating a battery current target based on at least one of the voltage V_cap and the movement detected at (a); and

adjusting a current drawn from the battery source by the energy-storage-device controller, according to the battery current target.

19. The method according to claim 18, wherein the calculated battery current target ranges between −

150 A and 300 A.

20. The method according to claim 19, further comprising:

detecting a power state of the machine, said power state being selected from the group consisting of a powered state and a shutdown state; and

wherein the battery current target is calculated according to;

if the voltage V_cap is lower than 30 V, setting the battery current target to 50 A;

if the voltage V_cap is greater than 30 V and the movement detected at (a) is the lifting movement, setting the battery current target to 200 A;

if the voltage V_cap is greater than 30 V and the movement detected at (a) is the lowering movement, setting the battery current target to 150 A;

if the voltage V_cap is greater than 30 V and the movement detected at (a) is the immobile movement, setting the battery current target to 150 A; and

if the power state detected corresponds to a shutdown state, setting the battery current target to −

150 A.