KR20070032962A - Electric golf car with low-speed regenerative braking - Google Patents

Abstract

A control system 10 for an electric vehicle / golf car comprising an electric decentralized motor having an armature winding 22 and a field winding 24. The system includes one MOSFET 34 connected in parallel across the armature windings connected to the freewheel diode 42 and the other 36 connected in series to the armature windings. When the motor is operating at or below the base speed, i.e. when the back EMF is below the supply power supply voltage, current flow is induced by immediately turning on the parallel MOSFET and shorting the armature coil. The current flow in the counterclockwise direction begins at the point where the series MOSFET is turned off, resulting in a large voltage spike across the motor and a reverse current flow into the battery. By rapidly turning Mospet on and off, current flow can be maintained, and regenerative braking can occur even at low speeds.

Description

ELECTRIC GOLF CAR WITH LOW-SPEED REGENERATIVE BRAKING}

1 is a schematic diagram of an electrical system for an electric vehicle having a half bridge architecture according to the present invention.

2 is a motoring / regeneration field map.

FIG. 3 is a schematic block diagram showing the control of armature current in the electrical system shown in FIG.

4 is a schematic block diagram showing a closed control loop for determining a speed reference value based on an accelerator pedal position.

5 is a schematic block diagram showing the armature current adjusted for speed and the monitored vehicle speed.

6 shows the relationship between the maximum armature current I _ARM and the vehicle speed.

Cross Reference of Related Applications

The present application is directed to US patent application Ser. No. 09 / 736,657, filed Dec. 14, 2000, entitled "Electric Golf Car With Slow Regenerative Braking," and Dec. 30, 1999. Priority is claimed on the basis of US Provisional Patent Application No. 60 / 173,638, filed "Personal Electric Golf Car."

The present invention relates to a control system for an electric golf car and, more particularly, to a control system for an electric golf car including a regenerative braking system having a half bridge rectifier that provides regenerative braking lower than the base speed.

All electric motors operate on the principle that two adjacent magnetic fields try to align towards each other. One way to generate a magnetic field is to prepare a wire winding and pass an electric current into the winding. If two windings with current flowing inside are close to each other, the magnetic fields of each winding tend to align towards each other. If the magnetic fields of the two windings are not aligned and are between 0 and 180 degrees, this tendency creates a rotational force between the two windings. If one of these windings is mechanically fixed to the shaft and the other is fixed to the outer housing, an electric motor is made. The rotational force generated between these windings is varied by the current flowing in the windings.

Unfortunately, the motor only makes one half revolution in one revolution before the magnetic field is aligned in one direction. Therefore, in order to continuously generate the rotational force so that the shaft of the motor can rotate more than 180 degrees, the two windings must always have an angle with respect to each other. A device that provides this functionality is called a commutator. The rectifier disconnects current from an active moving coil called an armature winding before the angle between the armature coil and the field coil connected to the housing becomes zero. 2 Reconnect to the armature winding. The end of the armature winding has contact surfaces known as commutator bars. Contact surfaces made of carbon called brushes are fixed to the motor housing. As the shaft of the motor rotates, the brush breaks contact with one set of bars and makes contact with the next set of bars. This process keeps the angle between the active armature winding and the field winding constant. Maintaining a constant angle between the magnetic fields maintains a constant torque while the motor is rotating.

If the windings move in a magnetic field, voltage and current are induced in the windings. If current passes through the field windings and the armature turns, the voltage and current are induced in the armature windings, effectively converting the motor into a generator. This has two important effects. When the motor is used to apply electric power to electric vehicles, such as an electric golf car called motoring, the rotation of the motor is called back EMF (electro-motive force) across the armature winding. Induces a voltage. This voltage increases together with the increase of the motor speed and the field current. When the back EMF is equal to the voltage across the terminals of the motor, the maximum speed is reached. Another effect is that if an electrical load is applied to the armature winding and the armature winding turns, the motor operates as a brake and a generator. This effect is known as regenerative braking. This is an electric motor and the torque generated is varied by the current in the field windings and the armature windings, the speed of which varies with the applied armature voltage.

Examples of such regenerative braking for electric golf cars are described in US Pat. No. 5,565,760, registered by Ball et al., US Pat. No. 5,814,958, registered by Journey, US Pat. No. 5,332,954, registered by Lankin. And US Patent No. 4,626,750, which is registered by Post.

The speed of electric vehicles is controlled by varying the voltage applied to the motor. At low voltage, the counter electromotive force of the motor reaches the applied voltage at low speed. First, insert resistors in series with the motor to lower the effective voltage. This is how the speed of the motor is controlled in the industry. Unfortunately, this method is very inefficient at low speeds.

This inefficiency is explained by Ohm's law and Kirchoff's current and voltage laws. Ohm's law is

V (voltage) = I (current) x R (resistance)

By the above formula

P (power) = I (current) xV (voltage)

In short, Kirchhoff's law states that if you add up all the voltages, you get zero and all the currents must be the same in a given loop.

According to Kirchhoff's law of current, the current through a cell, a resistor, an armature winding and a field winding in the motor circuit of an electric vehicle are all the same. Kirchhoff's law of voltage also adds voltage across resistors, armature windings and field windings to the battery voltage (eg 36V), and thus to zero for all voltages in the circuit.

Assume that under certain driving conditions (gradient, surface, tire pressure, load on the vehicle, desired speed) the current 100 A, the voltage of the motor (armature and field windings) is 18V. Torque varies with current, and speed varies with voltage. Analyze the circuit how much power is lost in the resistor. By Kirchhoff's law, the voltage across the resistor is given by

V _BATT = V _ARM + V _FIELD + V _RES

36 = 18 + V _RES

V _RES = 18 V

The current is 100A, so the power lost in the resistor by Ohm's law is

P _RES = I _RES XV _RES

P _RES = 100 X 18 = 1800 Watts

The power used by the motor by Ohm's law is

P = (V _ARM + V _FIELD ) x I

P = 18 x 100 = 1800 watts

This means that half of the power from the battery was lost to heating the resistor. Under these conditions, the speed control system uses half of the resistive system energy to achieve the same performance.

In a resistance system, resistance decreases as the pedal position increases toward speed increase. In speed control systems, the duty cycle increases as the pedal position increases. Both methods effectively control the voltage applied to the motor and the speed of the vehicle. The difference in efficiency becomes less important as it approaches the full throttle.

Conventional electric vehicles operate based on the principles described above, and there are other ways to control them. Standard electric golf cars use a series wound motor. Series motors have field windings with very heavy wire wound only a few times. To obtain the maximum torque, the armature and the accounting winding are connected in series. Some other electric vehicles use shunt wound motors, in which the field windings are formed by winding a lot of small wires. To obtain the maximum torque, the armature and the account winding are connected in parallel or have a "decentralized" configuration. The strength of the magnetic field produced by the windings varies with the number of windings and the current passing through the windings. To achieve the same magnetic field strength, decentralized motors require less current to pass through the field windings than comparable motors. For example, the magnetic field strength obtained at 300 amps (A) in a series motor can be obtained with only 15-20 amps (A) in a decentralized motor. There are also some noticeable differences with respect to the controller. Decentralized motors require less current to achieve the same magnetic field, making the field winding a small set of power components. This is called the separately excited control of the motor.

As described above, the counter electromotive force varies with the strength of the magnetic field, and the strength of the magnetic field varies the magnetic current. In a series motor, the armature current and the field current are equal, so that the relationship between the magnetic field strength and the armature current is in a linear relationship. In a separate excitation system, the field current is selected corresponding to a given armature current. As the field current decreases, the strength of the magnetic field decreases. Thus the counter electromotive force is lowered and increases the speed of the motor for a given armature current. This is called field weakening.

The field current is still active forward, and if the vehicle descends the hill backwards, it generates a reverse current that flows directly into the freewheel diode. Since the diode is like a short circuit in that direction, it acts like a brake that slows the motor at a very low speed. This type of braking is called plug braking.

If the vehicle is braked by releasing the accelerator for more than a certain amount of time, the controller breaks energy into the field windings and continues to monitor the speed sensor. If the vehicle starts to move without depressing the acceleration, the controller will apply energy to the field winding in the opposite direction of the vehicle's movement to start plug braking.

First, it is an object of the present invention to provide an electric golf vehicle and a method for controlling the speed of an electric vehicle including a control system of an electric vehicle capable of regenerative braking below a basic speed.

It is another object of the present invention to provide an electric golf vehicle and a speed control method for an electric vehicle including a control system of an electric vehicle, in which the control of the negative quadrant of the field map is possible because the armature current is monitored.

Another object of the invention is that since the motor speed varies with the armature voltage V _ARM , the armature pulse width modulation can be used to control the vehicle speed as opposed to the method of field current variation speed control in previous controllers. It is to provide an electric golf vehicle and a speed control method of the electric vehicle including a control system of the electric vehicle.

Another object of the present invention is to change the vehicle speed according to the throttle position input signal by comparing the speed reference value (determined by the position of the pedal) with the actual speed value detected by the speed sensor via a closed control loop. The armature pulse width modulation is adjusted to ensure that the speed is monitored and the regenerative armature current limit (I _MAX ) is reduced at low speeds to prevent sudden regenerative braking characteristics during low speed operation. It is to provide a speed control method of the electric golf car and the electric vehicle comprising a.

In order to achieve the above object of the present invention, the present invention provides an electric golf car comprising a braking system, a battery system and a decentralized motor, wherein the motor includes an armature winding and a field winding, and the golf vehicle is an H-bridge. A plurality of MOSFET elements electrically connected in a circuit and electrically connected to the field winding; And a plurality of MOSFETs electrically connected in a half H-bridge circuit, wherein a first MOSFET element is electrically connected in parallel with the armature winding and a second MOSFET element is electrically connected in series with the armature winding. A plurality of MOSFET elements; A freewheel diode electrically connected in parallel with the armature winding; a current sensor for measuring an armature current passing through the armature winding; a speed pedal position switch for determining a position of an accelerator pedal of the golf car and generating a speed reference signal; And a control system for switching the on / off of the first MOSFET element to control the armature current flowing through the armature winding to provide regenerative braking of the speed from base speed to zero in a golf car. It provides an electric golf car comprising a braking system and a battery system and a decentralization motor provided.

An armature pulse width modulation circuit for generating an armature pulse width modulated signal and a speed sensing circuit for determining the speed of the vehicle are further provided, wherein the pedal position switch determines the speed of the vehicle, and the speed sensing circuit detects the speed. Generating a signal, wherein the speed sensing signal and the speed reference signal are applied to an addition junction, and the addition junction generates a speed signal to be applied to the armature control circuit.

The pulse width modulated signal is applied to the second MOSFET.

The control system is characterized in that it comprises means for controlling the motor armature current between a minimum and a maximum as a function of speed.

The control system includes means for measuring the armature current in the negative quadrant of the field winding map, wherein the control system selects the field winding current for controlling the field winding based on the measured armature current.

The control system includes means for generating a field current, wherein the means for generating a field current includes an add junction point that responds to and sums the field current and the field current reference signal, and generates a pulse width modulated signal from the added signal. And a field pulse width modulation circuit to be generated.

The invention also relates to a speed control method of an electric vehicle comprising a decentralized motor having an armature winding and a field winding, comprising: connecting a first switching element in parallel to the armature winding of the motor: regenerative at or below the base speed of the motor A speed of an electric vehicle comprising a decentralized motor having an armature winding and a field winding, comprising turning on and off the switching element to control the armature current passing through the armature winding to provide braking Provide a control method.

The step of electrically connecting the first switching element is characterized in that it comprises a MOSFET element electrically connected in parallel to the armature winding.

And electrically connecting a second switching element in series with the armature winding.

And controlling the vehicle speed between the base speed of the motor and the speed zero (0).

Controlling the vehicle speed below the base speed includes controlling a pulse width modulated signal applied to the armature winding and sensing a position and vehicle speed of an accelerator pedal.

The step of controlling the vehicle speed may include applying the pulse width modulated signal to a switching element in electrical series with the armature winding.

And controlling the motor armature current between a minimum value and a maximum value as a function of speed.

Controlling the armature current includes combining the vehicle speed and the armature current to determine the armature current, determine the vehicle speed, and control the speed of the vehicle.

Measuring the armature current in the negative quadrant of the field map winding and controlling the field winding current based on the measured armature current.

As the present invention teaches and directs, a control system for an electric vehicle such as a golf car is disclosed, wherein the control system of the electric vehicle includes a plurality of metal oxide semiconductor field effect transistors (MOSFETs). Four Mospets make up a full H-bridge and two Mospets make up a half H-bridge. In half the H-bridge one mospet is electrically connected in parallel across the armature coils and the other in series with the armature coils. The MOSFETs connected in parallel across the armature wires comprise a freewheel diode.

When the motor is operating at or below the base speed, i.e., when the back EMF is below the supply voltage, current flow is induced by turning on the parallel MOSFET immediately and shorting the armature coils. Because of the inductance in the motor armature, the current flow in the counterclockwise direction starts at the point where the series MOSFET is turned off. The result is a large voltage spike across the motor and a reverse current flow into the battery. By using pulse width modulation technology to quickly turn parallel MOSFETs on and off, current flow is maintained and regenerative braking is achieved at low speeds.

In addition, control of the negative quadrant of the field map is made possible because the armature current is monitored. By varying the field current I _f to match the reference current I _ref , the field map curve can be maintained. In addition, since the motor speed changes with the armature voltage V _ARM , the armature pulse width modulated signal can be used to control the vehicle speed in a manner opposite to that of conventional controllers, namely field current variation speed control.

In addition, in the closed control loop, the speed reference value determined by the pedal position is compared with the actual speed value detected by the speed detector. Adjustments are made to the armature pulse width modulation signal to vary the vehicle speed in response to the maximum throttle position input signal. At low speeds, in order to prevent irregular regenerative braking characteristics, the speed is continuously monitored and the regenerative armature current limit I _MAX decreases at low speeds.

Further objects, advantages and features of the present invention will become apparent with reference to the following description and the accompanying drawings.

The following description of the preferred embodiment of the regenerative braking system of the electric golf car is illustrative and is not intended to limit the scope of the present invention, its application or use.

1 is a schematic layout view 10 of an electric system of an electric vehicle, wherein the electric golf vehicle includes a regenerative braking system according to an embodiment of the present invention. The layout 10 includes a battery system 12, a motor 14, and a control system 16. Typical battery system 12 includes a battery pack 18 having a plurality of individual batteries 20. In one embodiment, battery pack 18 includes six 6-volt batteries to add up to 36 volts. The battery 20 is a lead acid battery that is sufficiently discharged. The motor 14 comprises a motor armature winding 22 and a field winding 24. Windings 22 and 24 in the motor 14 act as inductors. This means that once a current flows through the windings 22, 24, the current will continue to flow.

A current detector 44 has been provided to measure the current flowing through the armature winding 22 in the control system 16. The current detector 44 may be a wire winding surrounding a hall effect integrated circuit. It is formed to put the Hall effect circuit in the magnetic winding loop, and the magnetic field it detects is proportional to the current I _ARM .

The control system 16 includes six power drive MOSFETs 26-36 and one capacitor 40. The MOSFETs 26-36 are practical switches capable of turn-on / turn-off 15,000 times per second. Within this specification, the term "mospet" may be one MOSFET or a plurality of Morphets connected in parallel controlled by one signal. The MOSFET 34 is connected to both ends of the motor armature winding 22 and includes a freewheel diode 42. The diode 42 acts like a valve to enable one-way passage of electricity. Thus, electricity flows only in the direction of the arrow indicated by the symbol on the diode. In a quarter-bridge armature circuit, the freewheel diode 42 consists of a separate device (element). However, in the configuration of the power supply MOSFET 34, the freewheel diode 42 was provided as an intrinsic semiconductor made of silicon.

Combining Mospets (26-32) results in H-bridges or full bridges. Combining Mospets (34) and (36) results in half bridges. The half bridge controller refers to the half bridge structure used for the motor armature winding 22 rather than the full bridge used for the field winding 24. The power driven MOSFETs 26-32 and the H-bridge structure are the same as in the known art. Characteristic of the system 10 is the use of two power MOSFETs 34 and 36 and is also associated with a motor armature winding 22 and in particular a power morse connected in parallel across the motor armature winding 22. The use of MOSFET 36 in conjunction with PET 34 and diode 42 and how they are driven. The conventional DC motor driving system used in the conventional electric vehicle includes only the series MOSFET 36 and the freewheel diode 42 under the motor armature winding 22.

The motor 14 is a decentralized motor because the armature winding 22 and the field winding 24 are connected in parallel at both ends of the two main batteries. This operation may, for example, be such that the series power MOSFET 36 of the armature winding 22 is turned on and the power supply MOSFETs 26 and 32 opposite the two field windings 24 are turned on. Do that at that time. In a conventionally excited system, the speed of the motor 14 is typically obtained by varying the field current. In the present invention, the pulse with modulation (PWM) of the armature current I _ARM is used to control the vehicle speed.

In this system, the logic circuit of the control system 16 controls the turn-on / turn-off of the MOSFETs 26-36. In order to control the effective voltage applied to the motor 14, the ratio of the total time that the MOSFETs 26-36 are turned on and the total time that is turned off is controlled. This is called the duty cycle. When the MOSFET 36 is turned on, the battery 20 is directly connected at both ends of the armature 22. By Kirchhoff's law, the voltage across the battery 20 and the voltage across the armature 22 are equal to 36 volts (V). Again, according to Kirchhoff's law, the current passing through the armature 22 and the battery 20 is the same. In the circuit, the current flows in the direction opposite to the direction of the arrow of the freewheel diode 42, and the freewheel diode 42 can be ignored under these conditions.

When the MOSFET 36 is turned off, the circuit including the battery 20 is cut off. However, since there is a current passing through the armature 22, the flow of current does not try to stop.

Freewheel diode 42 is part of the circuit. If the current continues to flow at the same speed in the same direction as before, the current will flow through the freewheel diode 42. The voltage across the diode 42 and the armature 22 will be zero but the current flowing as before. In the battery circuit, there is no current flow because the circuit is not complete. However, the battery voltage remains at 36V.

The voltage across the armature 22 is 36V when the MOSFET 36 is turned on and zero when the MOSFET 36 is turned off. The average voltage across the motor 14 is as follows.

V _ARM = (36V x workload cycle) + (0V x (1- workload cycle))

V _ARM = 36 V x workload cycle

Torque required to operate the vehicle determines the motor current. Since the battery current is the same as the motor current, when the MOSFET 36 is off, it is zero, and when it is on, the battery current is as follows.

I _BATT = (I _ARM x Workload Cycle) + (0A x (1-Work Cycle Cycle))

I _BATT = I _ARM x Workload Cycle

With the solid-state speed controller above, using a current of 100A and a voltage of 18V, the difference is:

V _ARM = 36 x workload cycle

18 = 36 x workload cycles

Workload Cycle = 50%

I _BATT = I _ARM x Workload Cycle

I _BATT = 100A x 50%

I _BATT = 50 A

Here, the power going out of the battery 20 and the power going into the armature 22 can be calculated by the power equation already described. As in the above example, the power of the motor is 1800 watts.

P _BATT = I _BATT x V _BATT

P _BATT = 50A X 36V = 1800 Watts

Table 1 summarizes the differences under these conditions for each of the two systems.

System type Motor power Battery power resistance 1800 Watt 3600 Watt Speed controller 1800 Watt 1800 Watt

For example, when the vehicle is going down a hill, the normal operation in the regenerative braking mode of the motor armature winding 22 is only present if the speed of the motor 14 is higher than the base speed of the motor 14. The base speed is the speed at which the back EMF equals the battery voltage. If the back EMF is equal to or less than the battery voltage, the energy generated by the motor 14 cannot flow into the battery pack 18 because the battery voltage is too high. To overcome this limitation, a power MOSFET 34 has been added along with the freewheel diode 42. If the speed of the car is slower than the basic speed, the battery pack 18 cannot be charged for the same reason as described above, and thus regenerative braking is not performed. To overcome this limitation, the MOSFET 34 is simply turned on. Since the potential difference across both ends is almost zero when the MOSFET 34 is fully energized, the motor 14 generates a large current, and this current simply passes through the MOSFET 34. Done. Since this brief current cannot stop immediately, a large voltage is generated that exceeds the normal back EMF, i.e. above the battery voltage. The armature winding 22 then pumps the energy into the battery pack 18 during the brief period. The brief period is equal to the time required for the high voltage of the motor 14 to fall from the highest to the battery voltage. Next, this process

The above process is performed hundreds or thousands of times per second to induce energy of the motor 14 so that the motor 14 generates a voltage high enough to generate a regenerative braking effect at both ends of the battery pack 18. Is repeated. Thus, the motor 14 gradually decreases in speed.

It is very important to apply strong braking to the motor 14 by the moss 34 by turning on the moss 34. It is a common way to brake a DC motor, but it is undesirable if the time is too long. It is therefore important to specialize this braking operation in one or more ways. However, the characteristics of the power MOSFET 34 require it to be turned on or off. Thus, in order to achieve a characteristic effect, it is necessary to change the armature pulse width modulation workload period. Table 2 below provides the values of the pulse width modulation workload periods for V _BATT , I _BATT , I _ARM , and V _ARM .

% Workload cycle V _BATT I _BATT I _ARM V _ARM 50 36 150 300 18 10 36 30 300 3.6 100 36 300 300 36 0 36 0 0 0

The armature voltage is reversed only when the series power MOSFET 36 is off in the normal running mode. At this time, i.e., when the series power MOSFET 36 is off and in the normal running mode, the current continues to flow and the armature voltage is reversed to push the current through the freewheel diode 42.

In the conventional electric golf car, the motor 14 causes the regenerative braking to occur when the speed of the vehicle is 16Km or more per hour. Regenerative braking does not occur below 16 km / h. The regenerative braking is also used to limit downhill vehicle speed. Even for safer driving, no regenerative braking occurs when the accelerator pedal pressure is relieved, even if the vehicle speed is 20.8 kilometers per hour (13 miles per hour).

An important advantage of the present invention is that the speed of the vehicle is reduced to a speed of at least 2 miles per hour using an accelerator pedal. Known controllers in the past limited the vehicle's speed only when the pedal was fully released. That is, if the accelerator pedal is lightly pressed, the speed of the vehicle reaches the maximum speed of the motor 14, and the regenerative braking automatically stops at the maximum speed of the motor. This is particularly undesirable where the slope is steep. In the present invention, the accelerator pedal operates in the same way as a vehicle having an internal combustion engine with manual transmission. That is, the accelerator pedal is used to directly adjust the low speed of the vehicle to form a relatively linear relationship between the position and the speed of the pedal. In other words, by using the accelerator pedal in the present invention, for example, the vehicle speed is adjusted to 12.8 km per hour (8 miles per hour), 9.6 km per hour (6 miles per hour), 8 km per hour (5 miles per hour) and the vehicle operator You can choose to release the pedal anywhere.

The maximum speed of the vehicle is a parameter determined by conventional controllers. This is the speed the vehicle will gain at ground level. When the vehicle reaches the top of the hill and starts descending the hill again, a typical conventional controller is set to limit its maximum speed even if gravity causes the vehicle to run faster as the vehicle descends the hill.

In summary, in the conventional driving system, pedaling is simply used to accelerate the vehicle from the basic speed to the maximum speed, and the motor cannot be controlled at all below the basic speed. However, the position of the pedal in the system of the present invention is such that it is possible to control the speed of the vehicle at any level from the speed near zero to the maximum speed set by the control system 16 and the motor 14. There may be a linear relationship between pedal position and vehicle speed. But it can also be nonlinear if desired. For example, in order to operate sensitively at low speeds, the counter electromotive force of the motor 14 increases with the speed of the motor and also with the increase of the field winding current. In a series motor, the motor armature winding 22 and the field winding 24 are connected in series, which ensures that the motor armature current and the field winding current cannot be controlled independently. The field winding current should always be the same. In a decentralized motor, the motor armature winding 22 and the field winding 24 are completely separated so that the currents can be regulated separately between the two circuits. Therefore, in order to reduce the counter electromotive force of the motor, it is necessary to reduce the field winding current. This gives motor control designers more flexibility to achieve the desired motor characteristics.

2 is a typical field map. Field map is a term widely used in the industry to describe the relationship between armature current and field current in decentralized motors. Each motor has a specific area of the field map for optimal performance. Operation too far from this area can seriously damage the motor.

In the upper right quadrant of the field map, the line 46 represents the performance of a series motor having a field current that functions as an armature current that is independently controlled. In a decentralized motor system, the field current and armature current can be controlled independently, resulting in a non-linear curve 56 as also shown in the upper right quadrant as shown in FIG. This special field map allows better performance under conditions that can be programmed in conventional controllers. However, conventional control techniques using the freewheel diode 42 and the quarter-bridge armature circuit do not provide control in the upper left quadrant of the fieldmap. However, the present invention provides a technique for operating in the upper left quadrant of the field map, such as line 58.

In a decentralized motor system with a known quarter bridge controller. The armature current can actually be measured because of the known resistance value of the power MOSFET 34 which is actually known. In other words, the armature current is measured by measuring the voltage across the power MOSFET 34. In the system of the present invention, the current detector 44 can measure the armature current I _ARM in the negative quadrant (left quadrant) of the field map. Next, according to the detected current value I _ARM , the controller corrects the I _f value from the graph. In the past, this armature current information could not be obtained simply, and therefore other factors based on this information could not be adjusted.

3 is a feedback loop 48 that includes a summing junction 50 that receives the field current reference input i _ref and generates an input signal to a field pulse width modulation (PWM) block 52. . The PWM block 52 generates a PWM field current. The pulse width modulated field current is applied to the current source 54 which generates the field current i _f . The current I _f is fed back to the addition junction 50. The pulse width modulated field current actually controls the average voltage, which results in or not obtaining the desired field current. The problem with the field winding is that the resistance changes with temperature. Thus, even if the applied voltage is the same, the field current will vary with temperature. By using the feedback loop of Fig. 3, the desired field current can be obtained regardless of the temperature. The field winding 24 also operates in a practical environment with a magnetic field or the like induced by an armature or others. The feedback system of FIG. 3 also considers other auxiliary factors that may destabilize the desired I _f signal.

An advantage of adjusting the operation of the negative quadrant of the field map of the motor 14 is that it operates more reliably under all conditions. Typically shunt DC motors are operating within the I _f I _ARM contrast conditions and scope. The motor 14 may be damaged if it is operated for a long time in a condition outside the range. Thus, the reliability and serviceability of the motor 14 may be subject to downhill regenerative conditions or other abnormalities where the motor 14 may deviate from the normal I _f / I _ARM , which is the desired operating range. In all cases involving environments, this is increased by guaranteeing the recommended I _f / I _ARM .

The problem of regenerative safe driving zones arises in large vehicles such as five-seater golf vehicles. This is because small two-seater golf vehicles generally do not run long enough to adversely affect the motor 14 in the undesirable I _f / I _ARM region. Also, on hilly or mountainous courses, the large vehicle tends to put a high stress on the motor.

4 is a block diagram 60 showing controlling the speed of a vehicle by using a magnetic pulse width modulated signal. The accelerator pedal position signal 62 is a speed reference signal, which is input to the addition junction 64. The actual speed 66 of the vehicle is sensed, which is also input to the addition junction 64. A feedback signal is provided by comparing the two signals and the feedback signal is applied as an input signal to the armature pulse width modulation block 68. This generates an appropriate output pulse width modulated signal that is applied to the serial MOSFET 36 in the motor armature winding 22, which modulates the speed of the vehicle. More generally, the armature pulse width modulation block 68 operates a series MOSFET 36 and a MOSFET 34 in parallel with the armature winding 22.

To achieve the desired speed of the motor, the voltage across the armature winding 22 must be adjusted. The control of the voltage across the armature terminal of the motor is determined by the operation of the power MOSFETs 34 and 36 for the armature winding 22. The MOSFETs operate in the preferred way to obtain the desired motor voltage. Given the current speed of the vehicle, which determines the speed of the motor 14, the desired voltage to be applied to the terminals of the motor, i.e. the reverse power, can be calculated, and the power MOSFETs 34 and 36 It works properly to get the additional voltage needed to increase the speed. By lowering the motor armature terminal voltage below the counter electromotive force, regenerative braking is induced. Thus, the voltage applied to the motor armature winding 22 is adjusted in the desired manner through the left or right quadrant of the field map.

The term "pedal up braking" is used in connection with a conventional decentralized motor control system. Basically, when the vehicle accelerator pedal is released, the control system 16 will actively perform regenerative braking until the motor 14 reaches a basic speed, for example 16 km per hour. Below the base speed, active control does not occur because the regenerative braking characteristic of the motor 14 cannot provide sufficient back electromotive force above the battery voltage. Thus, no regenerative braking. Since the present invention provides regenerative braking below the base speed of the motor 14, the term "pedal up braking" is used at a speed much lower than the base speed of the motor 14.

During low speed regenerative braking, if the control system allows a linear relationship between the maximum I _ARN and the speed, the vehicle speed decelerates very quickly when the pedal is released. Basically, this is similar to driving a vehicle during parking brake. Essentially, the vehicle is generally costly when the vehicle speed is above the speed indicated by the pedal position. In this improved system, if active regenerative braking is on, such regenerative braking will actually slow down the vehicle very quickly. These features also include regenerative braking below some setpoint low speed, which begins to cost money to drive the vehicle. The critical low speed is preferably between 3.2 km / h and 12.8 km / h (between 2 and 8 miles per hour) and 8 km / h (5 miles per hour) in hilly areas.

5 and 6 show how the armature current I _ARM is controlled between the minimum and maximum values as a function of speed. The maximum armature current is typically generated in regenerative braking mode and the current limit is designed to prevent the control system and the commutator 16 from overheating. Speed sensing system 72 includes an add junction 74 that accepts a speed sensing signal as input and receives a current signal from current sensing circuit 76 corresponding to current detector 44. The minimum armature current will be some value that does not cause excessive braking at zero or low speed.

As described above, the electric vehicle control system of the present invention has several advantages over the prior art. One of these benefits is regenerative braking at base speeds. If the motor 14 is operating below its base speed, i.e., its counter electromotive force is below the power supply voltage, the flow of current can be induced by immediately conducting the MOSFET 34 and shorting the armature winding 22. have. Because of the residual inductance in the motor 14, current flow in the counterclockwise direction begins at the point where the MOSFET 34 is turned off. As a result, a large voltage spike across the motor 14 occurs, resulting in reverse current flow to the battery pack 18. By turning the MOSFET 34 on and off at high speed, current flow can be maintained and regenerative braking can occur even at low speeds.

In addition, control of the negative quadrant of the field map is made possible because the armature current is monitored. By changing I _f to fit I _REF , the field map curve is maintained. Since the motor speed also varies with the armature voltage V _ARM , the armature pulse width modulation can be used to control the vehicle speed as opposed to the method of field current variation speed control in previous controllers. Also through the closed control loop, the speed reference value (determined by the position of the pedal) is compared with the actual speed value detected by the speed detector. Adjustment of the armature pulse width modulation is made to vary the vehicle speed in accordance with the throttle position input signal. And, to prevent sudden regenerative braking characteristics during low speed operation, the speed is continuously monitored and the regenerative armature current limit I _MAX decreases at low speed.

The foregoing discussions merely describe and disclose embodiments of the present invention. Those skilled in the art will be able to readily understand the present invention from the foregoing description and accompanying drawings and claims, and various changes, modifications and changes can be made without departing from the scope and spirit of the claims of the present invention. Can be done.

As described above, the electric golf car and the electric vehicle speed control method including the electric vehicle control system of the present invention has several advantages as compared to the prior art.

First, according to the present invention, it is possible to provide an electric golf vehicle and an electric vehicle speed control method including an electric vehicle control system capable of regenerative braking below a basic speed.

According to the present invention, it is possible to provide an electric golf vehicle and a speed control method for an electric vehicle including a control system of an electric vehicle, where the control of the negative quadrant of the field map is possible because the armature current is monitored.

In addition, according to the speed control method of the electric golf vehicle and the electric vehicle including the control system of the electric vehicle of the present invention, since the motor speed is changed in accordance with the armature voltage (V _ARM ), the armature pulse width modulation in the previous controllers It can be used to control the vehicle speed as opposed to the method of field current fluctuation speed control.

Also according to the present invention, through the closed control loop, the speed reference value (determined by the position of the pedal) is compared with the actual speed value detected by the speed sensor to vary the vehicle speed according to the throttle position input signal. To control the armature pulse width modulation and to prevent sudden regenerative braking characteristics during low speed operation, the speed is continuously monitored and the regenerative armature current limit (I _MAX ) includes an electric vehicle control system that decreases at low speeds. An electric golf car and a speed control method of the electric vehicle can be provided.

Claims (15)

An electric golf car comprising a braking system, a battery system and a decentralized motor, the motor comprising an armature winding and a field winding, The golf car, A plurality of MOSFET elements electrically connected in an H-bridge circuit and electrically connected to the field winding; And In a plurality of MOSFETs electrically connected in a half H-bridge circuit, a first MOSFET element is electrically connected in parallel with the armature winding and a second MOSFET element is electrically connected in series with the armature winding. A plurality of MOSFET elements; A freewheel diode electrically connected in parallel with the armature winding; A current detector for measuring an armature current passing through the armature winding; A speed pedal position switch for determining a position of an accelerator pedal of the golf car and generating a speed reference signal; And A control system for switching on / off of the first MOSFET element to control the armature current flowing through the armature winding to provide regenerative braking of the speed from base speed to zero in a golf car. Electric golf car including brake system, battery system and decentralization motor provided The armature pulse width modulation circuit for generating an armature pulse width modulated signal and a speed sensing circuit for determining the speed of the vehicle are further provided, wherein the pedal position switch determines the speed of the vehicle. The speed sensing circuit generates a speed sensing signal, wherein the speed sensing signal and the speed reference signal are applied to an addition junction, and the addition junction generates a speed signal to be applied to the armature control circuit. Electric Golf Car Including System And Decentralization Motor 3. The electric golf car of claim 2, wherein the pulse width modulated signal is applied to the second MOSFET element. 2. The electric golf vehicle of claim 1, wherein the control system includes means for controlling the motor armature current between a minimum and maximum value as a function of speed. The method of claim 1, wherein the control system comprises means for measuring the armature current in the negative quadrant of the field winding map, the control system selecting a field winding current to control the field winding based on the measured armature current. An electric golf car comprising a braking system, a battery system, and a decentralized motor, characterized in that. 2. The control system of claim 1, wherein the control system comprises means for generating a field current, wherein the means for generating field current includes an add junction point that responds to and sums the field current and the field current reference signal, and adds the added signal. An electric golf vehicle comprising a braking system, a battery system and a decentralized motor, comprising a field pulse width modulation circuit for generating a pulse width modulated signal from the field. In the speed control method of an electric vehicle comprising a decentralized motor having an armature winding and a field winding, Connecting a first switching element in parallel to the armature winding of the motor: Decentralization with the armature winding and the field winding, comprising turning on and off the switching element to control the armature current passing through the armature winding to provide regenerative braking below the base speed of the motor. Speed control method of an electric vehicle comprising a motor. 8. The method of claim 7, wherein the step of electrically connecting the first switching element comprises connecting a MOSFET element in electrical parallel to the armature winding. 8. The method of claim 7, further comprising the step of electrically connecting a second switching element to the armature winding in series. 8. The method of claim 7, further comprising the step of controlling the vehicle speed between the base speed of the motor and the speed zero (0). 11. The method of claim 10, wherein controlling the vehicle speed below the base speed comprises controlling a pulse width modulated signal applied to the armature winding and sensing the position of the accelerator pedal and the vehicle speed. How to control the speed of an electric vehicle. 11. The method of claim 10, wherein controlling the vehicle speed comprises applying the pulse width modulated signal to a switching element in electrical series with the armature winding. 8. The method of claim 7, further comprising controlling the motor armature current between a minimum value and a maximum value as a function of speed. The method of claim 13, wherein controlling the armature current includes combining the vehicle speed and the armature current to determine the armature current, determine the vehicle speed, and control the speed of the vehicle. Speed control method of electric vehicle. 8. The method of claim 7, further comprising the step of measuring the armature current in the negative quadrant of the field map winding and controlling the field winding current based on the measured armature current. .

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