IE83341B1 - A power control device - Google Patents
A power control deviceInfo
- Publication number
- IE83341B1 IE83341B1 IE1999/0786A IE990786A IE83341B1 IE 83341 B1 IE83341 B1 IE 83341B1 IE 1999/0786 A IE1999/0786 A IE 1999/0786A IE 990786 A IE990786 A IE 990786A IE 83341 B1 IE83341 B1 IE 83341B1
- Authority
- IE
- Ireland
- Prior art keywords
- motor
- power
- control device
- speed
- power control
- Prior art date
Links
- 230000000694 effects Effects 0.000 claims description 6
- 230000001276 controlling effect Effects 0.000 claims description 5
- 230000000051 modifying Effects 0.000 claims description 4
- 230000001105 regulatory Effects 0.000 claims description 3
- 230000001965 increased Effects 0.000 description 3
- 230000000414 obstructive Effects 0.000 description 2
- 230000002035 prolonged Effects 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000000295 complement Effects 0.000 description 1
- 230000000875 corresponding Effects 0.000 description 1
- 230000001186 cumulative Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 230000002708 enhancing Effects 0.000 description 1
- 230000003116 impacting Effects 0.000 description 1
- 230000002452 interceptive Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
Description
A power control device
This invention relates to a power control device and, in particular,
to a power control device for use in a vehicle powered by an electric
motor.
There are many examples of vehicles which can be, and are,
powered by electric motors. These include wheelchairs, mopeds, golf
trolleys and the like.
Using the example of a golf trolley, this will usually comprise a
motor to drive the wheels via an arrangement of gears and a power
source for the motor, typically a battery.
The trolley is usually controlled by one or more controls which
can be adjusted manually by the user to vary the speed of the motor in
some way or other. In their simplest form these controls will comprise
an on/off switch and some type of “throttle” controlling the power
supplied to the motor. A drive module connects the controls, the power
source and the motor in order to provide the appropriate impulses to the
power source in response to the settings of the controls to adjust the
speed of the motor.
Conventional motorised golf trolleys do however suffer from a
number of drawbacks, caused by a variety of circumstances, resulting in
damage to motor, power source and gears. Examples of situations which
can lead to damage include:
sudden stalls caused, for example, by encountering an obstacle.
The sudden increase in current can lead to permanent damage to
the motor windings within a few seconds. In a prolonged stall the
current build up can also detrimentally affect the power source;
the trolley being held stationary on an incline by applying a low
power setting. Because this stall effect is usually not detected, it is
the largest single cause of damage in conventional golf trolleys
and can cause serious cumulative damage to the motor with
eventual failure; and
sudden start shock caused by turning the power setting to full on
from off. This causes damage to both motor and gears due to the
sudden transition from off to full on and, because of a temporary
short circuit from motor to the power source, damage of the latter
can also occur. Similar effects occur when the power is suddenly
turned off.
In addition, conventional golf trolleys require the user to
repeatedly adjust the controls for moving the trolley forward in order to
maintain a desired speed or to move the trolley even a short distance.
This can be awkward and tiresome.
Similar concerns apply to all vehicles driven in this manner.
Although there are individual solutions available for solving these
problems, such as sensors for monitoring motor movement and/ or
detecting current surge, bimetallic strips for reacting to overheating,
sophisticated cruise control systems and the like, these tend to increase
significantly the cost of the vehicle particularly in the case of smaller
vehicles such as golf trolleys.
There is therefore a need for a power control device which will
avoid damage to the power and drive elements of the vehicle and at the
same time increase user comfort without prohibitively impacting on
production costs.
It is the object of the present invention to provide a power control
device which will address these needs.
The present invention therefore provides a power control device
for use in a vehicle powered by an electric motor connected to a power
source therefor, which comprises means for detecting and measuring
fluctuations in the current flow to the motor in use, means for
determining the speed of the motor on the basis of the measured
fluctuations, and means for controlling the speed of the motor such that
the relationship between the speed of the motor and the power being
supplied thereto is maintained within predetermined limits.
Determining motor speed on the basis of detection and
measurement of fluctuations in the current flowing to the motor
eliminates the need for separate sensors.
Providing means whereby the speed of the motor and the power
supplied thereto are maintained within predetermined limits enables
inappropriate and potentially damaging extremes of power to be
avoided.
Preferably, the means for determining the speed of the motor and
the means for controlling the speed of the motor form part of a feedback
system which adjusts the level of power supplied to the motor from the
power source.
In this way switching systems can be employed which enable
adjustments to the power supplied to the motor to be made virtually
instantaneously upon determining the motor speed.
Typically, the fluctuations in the current are those due to changes
in the magnetic attraction/repulsion effect as the rotor poles pass
towards and away from the stator poles in the motor.
This has the advantage that the fluctuations used to determine the
speed are signals which are generated by an electric motor in normal
operation.
Any suitable electronic component can be used to detect and
measure the fluctuations and the choice thereof will be evident to the
skilled person.
The amplitude of such fluctuations will typically be very small
usually in the microvolt range. For example, in the case of fluctuations
resulting from the attraction/repulsion effect they are in the range of
between 1kHz and 40kHz. It is therefore preferred that the fluctuations
in current are amplified before reaching the feedback system.
This amplification allows minor differences to be more readily
and precisely determined thus providing enhanced accuracy and
reliability.
Preferably, the feedback system incorporates a micro-controller.
In this micro-controller signals from the key components in the drive
and power systems are received and read, appropriate responses to these
signals computed and impulses provided back to the key components.
Typically such a micro-controller will be in the form of a programmable
microchip.
Micro-controllers of this general type will be known to the skilled
person who will be able to program the same to carry out the functions
required in a power control device according to the present invention.
In order to minimise the risk of damage occurring to the elements
of the power and drive systems, the time during which extreme
conditions obtain should be kept as short as possible without interfering
with the normal functioning of the vehicle.
Therefore, in a preferred embodiment of the invention, the
predetermined limits are chosen such that the supply of power from the
power source is cut off if the speed of the motor and the power being
supplied thereto fail to conform to the predetermined limits within a
predetermined time period.
Preferably, the predetermined time period is shorter than the time
after which damage would occur to the motor, to the power source or to
other components of the vehicle if the supply of power were not cut off.
The actual length of the predetermined time period will depend on
the specifications of the particular power and drive elements chosen.
Preferably, the power source is a battery, especially a
rechargeable battery. In order to minimise production costs a standard
twelve volt dry cell battery for use with a corresponding electric motor
can be employed.
It is preferred that the power is transferred from the power source
to the motor as a series of on/off pulses of modulated width such that
the ratio of the time during which the power to the motor is on to the
time when it is off determines the speed of the motor.
In this manner the length of time during which the motor is
subjected to current from the power source within a fixed time period
can be regulated such that it is always commensurate with the level of
power required to achieve or maintain the desired speed or a measured
speed. This effectively eliminates the risk of the motor being subjected
to prolonged bursts of excessive power or sudden switching off of
power. This could otherwise occur, particularly in situations where the
vehicle comes to a sudden unexpected stop or where a user moves
abruptly to a full on or full off position on a manual control, if present.
The pulse speed preferably lies between 10 kHz and 50 kHz,
especially between 25 kHz and 35 kHz. .5
In the power control device according to the invention, it is
preferred that means are provided which enable a user of the vehicle to
stop and start the vehicle and to select a desired constant motor speed.
Preferably the means is an analog switch, the precise setting of
which is converted to a digital signal which is passed to the power
control device.
A preferred such switch is a potentiometer.
Providing such user control means can enable a user of the
vehicle to start and stop the vehicle, to select a desired constant speed
(“cruise control”), to move the vehicle a prescribed distance or to select
other appropriate functions.
In order to enhance the convenience of the vehicle, the power
control device will preferably include means that allow the level of
power supplied to the motor to be adjusted so as to permit the vehicle to
travel a pre-determined distance followed by an adjustment of the level
of power to cause the vehicle to stop.
Such a feature is particularly useful in golf trolleys as it will
enable the user to set the vehicle to move a few yards independently and
then come to a stop without the need for the user to have her or his
hands on the controls.
It is further preferred that the predetermined limits are chosen
such that the power being supplied to the motor at a given speed does
not significantly exceed that which the motor would be expected to use
when travelling constantly and unhindered at that same speed.
This feature not only enables the power control device to maintain
a constant speed as chosen by the user but allows for elimination of
excesses of current which are out of step with the speed of the motor
and which if unchecked would cause damage to the power or drive
elements of the vehicle.
Preferably, the predetermined limits are chosen such that the
power being supplied to the motor will cut off after a predetermined
time period unless the motor speed has reached a certain minimum
value.
This feature is particularly intended to prevent too high a level of
power flowing to the motor for a period which would be long enough to
cause damage to either the motor or gears themselves or to the power
source through possible short circuit effects. Such situations include in
particular those where the Vehicle meets an obstruction or where a user
inadvertently or intentionally uses the motor to maintain the vehicle in a
stationary position on a hill.
It is also preferred that the predetermined limits are chosen such
that the rate of increase or decrease in the level of power supplied to the
motor remains under control independently of any changes in settings
applied by the user.
This feature can be used for example to prevent damage being
caused to the motor and gears and/or the power source in situations
where a user moves a manual control switch to a full on or full off
position suddenly rather than gradually.
As mentioned herein, the power control device according to the
invention can be employed in any motorised vehicle which is driven by
an electric motor connected to a power source. Examples of such
devices include wheelchairs, lawnmowers, mopeds, golf carts and the
like.
The power control device is particularly useful where the vehicle
is a golf trolley. These vehicles are also known as power caddies and are
designed to carry a golf bag with a complement of clubs.
It is an advantage of the power control device according to the
invention that it can be incorporated into an existing design of a
motorised vehicle in place of the original power control device with
little, if any, need to modify the remaining elements and systems of the
vehicle.
In general terms the invention also concerns a method of
regulating the speed of a vehicle powered by an electric motor
connected to a power source therefor, which comprises:
a) detecting and measuring fluctuations in the current flow to the
motor in use;
b) determining the rotational speed of the motor on the basis of
the measured fluctuations;
c) adjusting the power supply to the motor in response to the
determined speed of the motor, such that the relationship
between the speed of the motor and the power being supplied
thereto is maintained within predetermined limits.
The invention will be further illustrated by the following
description of embodiments thereof, given by way of example only with
reference to the accompanying drawings, in which:
Fig. 1 is a block diagram representing the key elements in
the power control device according to the invention as
installed in a golf trolley and their relationship with each
other and with the components of the drive and power
systems.
Fig. 2 is a graph of power (volts) versus time representing
the transfer of power from the power source to the motor.
Fig. 3 is a flowchart providing a schematic representation
of the operation of the power control device of Fig. 1.
In Fig 1 there is indicated generally at 10 a schematic
representation of a power control device according to the invention.
The power control device 10 is connected between a direct
current motor 11 and a 12V dry cell battery 12 having a positive
terminal 13 and a negative terminal 14. A manual speed control 15, in
the form of a potentiometer, is also connected to the power control
device 10.
The motor 11 and the battery 12 are connected to the power
control device 10 via a drive switching unit 16 and a detector 17 for
detecting microvolt fluctuations in the current provided to the motor 30
from the battery 12. The detector 17 is connected to an amplifier 18
where the microvolt fluctuations are amplified before being received
and read by a micro-controller 19. The micro-controller 19 is also
connected to the drive switching unit 16. The manual speed control 15 is
connected to the power control device 10 through the micro-controller
19.
The micro-controller 19 compares the actual speed of the motor
11 with the power setting and adjusts the power accordingly by way of
feedback until the desired speed is attained.
The micro-controller 19 switches the battery 12 to the motor 11
through the drive switching unit 16 using pulse width modulation.
In Fig. 2 the supply of power from the battery 12 to the motor 11
by pulse width modulation is illustrated in graphic form. On the ordinate
the power supply to the motor 11 from the battery 12 is shown in volts
with OV representing off and 5V representing full on. The arrows along
the abscissa mark off equal time periods. The ratio of on to off per unit
time determines the speed of the motor. The graph indicates speed
increasing from zero to full speed, with pairs of peaks indicating
intermediate speed settings.
Fig. 3 is a flowchart in which certain key functions of the power
control device are indicated as boxes. Diamond-shaped boxes indicate
points where determinations of alternatives are made and rectangular
boxes indicate actions contingent upon such determinations or settings
of components. Arrows indicate the direction of flow of information and
instruction.
In use, these functions operate as follows. After setting up the
trolley with the manual speed control 15 in an “off” or “reset” setting a
user shifts the manual speed control 15 to a desired “on” setting. This
setting will be received and read by the micro-controller 19 and
compared with the speed of the motor 11 calculated in the micro-
controller 19 based upon the data received from the detector 17 through
the amplifier 18. If the correct speed has not been achieved, the micro-
controller 19 will determine whether the speed is too fast or too slow.
Based upon this information a signal will be passed from the micro-
controller 19 to the drive switching unit 16 which will decrease or
increase the power supplied to the motor 11 from the battery 12 to
decrease or increase the motor speed. The micro—controller 19 will then
continue to monitor the speed of the motor 11 and compare signals until
the desired speed is achieved.
In the case where an increase in speed has been computed, the
micro—contro1ler 19 will check the motor speed and if the speed has not
increased will check again after 4 seconds. In the event that the speed
has still not increased upon this second check, the micro—controller 19
will cease transmitting to the drive switching unit 16 and power will
cease to be supplied from the battery 12 to the motor 11.
Such a cessation of power supply would take place for example
where the motor 11 is unable to attain the desired speed due to the
trolley being unable to move forward because of an obstruction or the
like.
Claims (22)
1. A power control device for use in a vehicle powered by an electric motor connected to a power source therefor, which comprises means for detecting and measuring fluctuations in the current flow to the motor in use, means for determining the speed of the motor on the basis of the measured fluctuations, and means for controlling the speed of the motor such that the relationship between the speed of the motor and the power being supplied thereto is maintained within predetermined limits.
2. A power control device according to Claim 1, wherein the means for determining the speed of the motor and the means for controlling the speed of the motor form part of a feedback system which adjusts the level of power supplied to the motor from the power source.
3. A power control device according to Claim 1 or 2, wherein the fluctuations in the current are those due to changes in the magnetic attraction/repulsion effect as the rotor poles pass towards and away from the stator poles in the motor.
4. A power control device according to any preceding claim, wherein the fluctuations are in the range of between lkHz and 40kHz.
5. A power control device according to any one of Claims 2 to 4, wherein the fluctuations in current are amplified before reaching the feedback system.
6. A power control device according to any one of Claims 2 to 5, wherein the feedback system incorporates a micro—controller.
7. A power control device according to any preceding claim, wherein the predetermined limits are chosen such that the supply of power from the power source is cut off if the speed of the motor and the power being supplied thereto fail to conform to the predetermined limits within a predetermined time period.
8. A power control device according to Claim 7, wherein the predetermined time period is shorter than the time after which damage would occur to the motor, to the power source or to other components of the vehicle if the supply of power were not cut off.
9. A power control device according to any preceding claim, wherein the power source is a battery.
10. A power control device according to any preceding claim, wherein power is transferred from the power source to the motor as a series of on/off pulses of modulated width such that the ratio of the time during which the power to the motor is on to the time when it is off determines the speed of the motor.
11. A power control device according to Claim 10, wherein the pulse speed lies between 10 kHz and 50 kHz.
12. A power control device according to Claim 10 or 11, wherein the pulse speed lies between 25 kHz and 35 kHz.
13. A power control device according to any preceding claim, wherein means are provided which enable a user of the vehicle to stop and start the vehicle and to select a desired constant motor speed.
14. A power control device according to Claim 13, wherein the means is an analog switch, the precise setting of which is converted to a digital signal which is passed to the power control device.
15. A power control device according to Claim 14, wherein the switch is a potentiometer.
16. A power control device according to any preceding claim, which includes means that allow the level of power supplied to the motor to be adjusted so as to permit the vehicle to travel a pre- determined distance followed by an adjustment of the level of power to cause the vehicle to stop.
17. A power control device according to any preceding claim, wherein the predetermined limits are chosen such that the power being supplied to the motor at a given speed does not significantly exceed that which the motor would be expected to use when travelling constantly and unhindered at that same speed.
18. A power control device according to any preceding claim, wherein the predetermined limits are chosen such that the power being supplied to the motor will cut off after a predetermined time period unless the motor speed has reached a certain minimum value.
19. A power control device according to Claim 13, wherein the predetermined limits are chosen such that the rate of increase or decrease in the level of power supplied to the motor remains under control independently of any changes in settings applied by the user.
20. A power control device according to any preceding claim, wherein the vehicle is a golf trolley.
21. A method of regulating the speed of a vehicle powered by an electric motor connected to a power source therefor, which comprises: a) detecting and measuring fluctuations in the current flow to the motor in use; b) determining the rotational speed of the motor on the basis of the measured fluctuations; c) adjusting the power supply to the motor in response to the determined speed of the motor, such that the relationship between the speed of the motor and the power being supplied thereto is maintained within predetermined limits.
22. A power control device according to Claim 1, substantially as hereinbefore described with particular reference to and as illustrated in
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IE1999/0786A IE83341B1 (en) | 1999-09-21 | A power control device | |
GB0022923A GB2357163B (en) | 1999-09-21 | 2000-09-19 | A power control device |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IE1999/0786A IE83341B1 (en) | 1999-09-21 | A power control device |
Publications (2)
Publication Number | Publication Date |
---|---|
IE990786A1 IE990786A1 (en) | 2001-04-04 |
IE83341B1 true IE83341B1 (en) | 2004-03-10 |
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