KR20020077350A - Electric golf car with low-speed regenerative braking - Google Patents

Abstract

A control system (10) for an electric vehicle / golf car comprising an electromotive deceleration motor having an armature winding (22) and a field winding (24). The system includes one mosfet 34 connected in parallel across the armature winding connected to the freewheeling diode 42, and another mosfet 36 connected in series to the armature winding. When the motor is operating below the fundamental speed, that is, when the counter electromotive force is below the supply voltage, the parallel flow is immediately turned on and the current flow is induced by shorting the armature coil. A counter-clockwise current flow is thus initiated at the point where the serial MOSFET is turned off, resulting in a large voltage spike across the motor and a reverse current flow into the battery. Current flow can be maintained by rapidly turning the mosfet on and off, and regenerative braking can occur at lower speeds.

Description

ELECTRIC GOLF CAR WITH LOW-SPEED REGENERATIVE BRAKING [0002]

Every electric motor operates based on the principle that two adjacent magnetic fields try to align with each other. One way to generate a magnetic field is to prepare the wire windings and pass current into the windings. If two windings with current flow in close proximity 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 will create 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 produced. The rotational force generated between these windings is varied by the current flowing in the windings.

Unfortunately, this motor only makes half a turn during one rotation before the magnetic field aligns in one direction. Therefore, in order to continuously generate the rotational force so that the shaft of the electric motor can rotate at 180 degrees or more, 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 interrupts the current from the active moving coil, called the 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 termination of the armature winding has contact surfaces known as commutator bars. Contact surfaces made of carbon, called brushes, are secured to the motor housing. As the axis of the motor rotates, the brushes break contact with one set of bars and come into contact with the next set of bars. This process keeps the angle between the active armature winding and the field winding constant. A constant angle is maintained between the magnetic fields to maintain a constant torque during the rotation of the motor.

If the winding moves in a magnetic field, the voltage and current are induced in the winding. If the current passes through the field winding and the armature winding is turned, the voltage and current are induced in the armature winding to effectively turn the motor into a generator. This has two important effects. When the motor is used to power 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 Lt; / RTI > This voltage is increased together with the increase of the speed of the motor and the field current. When the counter electromotive force 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 is turned, the motor acts as a brake and a generator. This effect is known as regenerative braking. This is an electric motor and the generated torque is varied by the current in the field winding and the armature winding, and the speed varies depending on the applied armature voltage.

Examples of such regenerative braking for electric golf cars are disclosed in U.S. Patent No. 5,565,760, registered by Ball et al., U.S. Patent No. 5,814,958, registered by Journey, U.S. Patent No. 5,332,954, registered by Lankin, And U. S. Patent No. 4,626, 750, which is hereby incorporated by reference.

The speed of the electric vehicles is regulated by varying the voltage applied to the motor. At low voltage, the motor's back EMF reaches a voltage applied at low speed. First, resistors are inserted into the motor in series to lower the effective voltage. This is how the industry controls the speed of the motor. 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 as follows.

V (voltage) = I (current) xR (resistance)

By the above equation

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

In short, Kirchhoff's law is to add all voltages to zero and all currents must be the same in a given loop.

By Kirchhoff's current law, the current through the battery, resistor, armature winding and field winding in the motor circuit of an electric vehicle are all the same. Also, by Kirchhoff's voltage law, the voltage across the resistor, armature winding, and field winding is added together to become the battery voltage (for example, 36V) and therefore zero when all the voltages in the circuit are added.

It is assumed that the current of 100A and the voltage of the motor (armature and field winding) are 18V under certain driving conditions (gradient, surface, tire pressure, load applied to the vehicle, desired speed). Torque varies with current, and speed varies with voltage. Analyze the circuit to see 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 = 18V

The current is 100A, so the power dissipated 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 according to Ohm's law is as follows.

P = (V _ARM + V _FIELD ) x I

P = 18 x 100 = 1800 watts

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

In a resistive system, the resistance decreases as the pedal position increases toward increasing speed. In a speed control system, 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. A standard electric golf car uses a series wound motor. Direct motors have field windings where very heavy wires are wound only a few times. To obtain maximum torque, the armature and the account winding are connected in series. Some other electric vehicles use shunt wound motors, and the field windings in these decentralized motors are formed by winding very much with small wires. To obtain maximum torque, the armature and the account winding are connected in parallel or have a " decentralized " configuration. The intensity of the magnetic field generated by the winding changes in accordance with the number of windings and the current passing through the windings. To obtain the same magnetic field strength, a decentralized motor requires less current to pass through the field winding than the direct motor. For example, the magnetic field strength obtained at 300 amperes (A) for direct motors is obtained with only 15-20 amperes (A) for decentral motors. There are also some noticeable differences for the controller. In decentralized motors, a small current is required to obtain the same magnetic field, so the field winding can be made into a small set of power components. This is called a separately excited control of the motor.

As described above, the counter electromotive force varies with the intensity of the magnetic field, and the intensity of the magnetic field varies the magnetic current. In direct electric motors, the armature current and the field current are the same, 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 back EMF is lowered and the motor speed is increased with respect to the given armature current. This is called field weakening.

The field current is still active forward, and if the vehicle comes back down the hill, it will generate a reverse current that flows directly into the freewheel diode. Since the diode is like a short circuit in that direction, it behaves like a brake that decelerates the motor at very low speeds. This type of braking is called plug braking.

If the vehicle is braked by releasing the accelerator for a certain period of time or longer, the controller interrupts the energy to the field winding and continues to monitor the speed sensor. If the vehicle starts to move without depressing the acceleration, the controller will energize the field winding in the opposite direction of the vehicle motion initiating the plug braking.

Cross reference of related application

This application claims priority to U.S. Patent Application Serial No. 09 / 736,657, filed on December 14, 2000, entitled " Electric Golf Car with Low Speed Regenerative Braking, "Quot; U.S. Patent Application Serial No. 60 / 173,638, entitled " 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 comprising a regenerative braking system having a half bridge rectifier that provides regenerative braking below the base speed.

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

Figure 2 is a motoring / regeneration field map.

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

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

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

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

According to the teachings of the present invention, 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). The four mosfets constitute a complete H-bridge, and the two mosfets constitute a half H-bridge. In half-H-bridges, one mosfet is connected electrically in parallel across the armature coil and the other in series with the armature coil. The mosfet connected in parallel across the armature wire includes a free wheel diode.

When the motor operates below the basic speed, that is, when the counter electromotive force is equal to or lower than the supply voltage, the parallel flow is immediately turned on, and the current flow is induced by shorting the armature coil. Because of the inductance in the motor armature, the current flow in the counterclockwise direction starts at the point where the serial MOSFET is turned off. As a result, a large voltage spike across the motor is generated and a reverse current flows into the battery. By rapidly turning on and off the parallel MOSFET using pulse width modulation techniques, current flow is maintained and regenerative braking is achieved at low speeds.

In addition, control of the negative quadrant of the field map is possible because 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. Also, since the motor speed varies with the armature voltage V _ARM , the armature pulse width modulated signal can be used to control the vehicle speed in a manner that is contrary to the method of conventional controllers, i.e. field current swing speed control.

Also, in the closed control loop, the speed reference value determined by the pedal position is compared with the actual speed value sensed by the speed sensor. An adjustment is made to the armature pulse width modulated signal to vary the vehicle speed according to the maximum throttle position input signal. To prevent irregular regenerative braking characteristics at low speeds, the speed is continuously monitored and the regenerative armature current limit (I _MAX ) is reduced at low speeds.

Other objects, advantages and features of the present invention will become apparent from the following description and accompanying drawings.

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

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic layout 10 of an electrical system for an electric vehicle, which comprises 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. A typical battery system 12 includes a battery pack 18 having a plurality of individual batteries 20. In one embodiment, the battery pack 18 includes six 6-volt batteries to total 36 volts (V). The battery 20 is a lead-acid battery which is sufficiently discharged. The motor (14) includes a motor armature winding (22) and a field winding (24). The windings 22 and 24 in the motor 14 act as inductors. This means that once the current flows through the windings 22 and 24, the current will continue to flow.

A current sensor 44 was provided to measure the current flowing through the armature winding 22 within the control system 16. [ The current sensor 44 may be a wire winding surrounding the Hall effect integrated circuit. This is configured to place a Hall effect circuit within the magnetic winding loop, and the magnetic field it detects is proportional to the current I _ARM .

The control system 16 includes six power-driven MOSFETs (MOSFETs) 26-36 and one capacitor 40. The MOSFET 26-36 is a practical switch that can turn-on / turn-off 15,000 turns per second. Within this specification, the term " mosfet " may be a mosfet or may be a plurality of motets connected in parallel controlled by a single 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 that allows one-way flow of electricity. Therefore, electricity flows only in the direction of the arrow shown in the symbol of the diode. In the 1/4 bridge armature circuit, the freewheeling diode 42 is composed of a separate device (element). However, in the configuration of the power MOSFET (34), the freewheeling diode (42) is provided as an intrinsic semiconductor made of silicon.

Combining the mosfet (26-32) results in an H-bridge or a full bridge, and combining the mosfet (34) and (36) results in a half bridge. The half bridge controller refers to the half bridge structure used in the motor armature winding 22, not the full bridge used in the field winding 24. The power-driven MOSFET 26-32 and the H-bridge structure are the same as known techniques. What is characteristic of the system 10 is the use of two power MOSFETs 34 and 36 and also a power mosewhich is connected in parallel with the motor armature windings 22, The use of the mosfet 36 associated with the PET 34 and the diode 42, and the way they are driven. In a conventional DC motor drive system used in a conventional electric vehicle, only the series mosfet 36 and the freewheel diode 42 below the motor armature winding 22 are included.

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 be performed, for example, when the series power MOSFET 36 of the armature winding 22 is turned on and the opposite power MOSFET 26 (32) of the two field windings 24 is turned on And so on. In a separate excited system, the speed of the motor 14 is typically obtained by varying the field current. In the present invention, pulse with modulation (PWM) of the armature current I _ARM is used to control the vehicle speed.

In this system, the logic circuitry of the control system 16 controls turn-on / turn-off of the MOSFET 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 on and off is controlled. This is called the duty cycle. When the MOSFET 36 is turned on, the battery 20 is directly connected to both ends of the armature 22. By Kirchhoff's law, the voltage across the battery 20 and the voltage across the armature 22 is equal to 36 volts (V). Also, the current passing through the armature 22 and the battery 20 is also the same according to Kirchhoff's law. In the circuit, the current flows in the direction opposite to the direction of the arrow of the free wheel 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 stop.

The freewheeling 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 free wheel diode 42. The voltage across the diode 42 and the armature 22 will be zero, but the current flowing is the same as before. In the battery circuit, there is no current flow because the circuit is not complete. However, the battery voltage is maintained 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 both ends of the motor 14 is as follows.

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

V _ARM = 36V x Workload cycle

A torque required to operate the vehicle determines the motor current. The battery current is zero when the MOSFET 36 is off and is on when the battery current is equal to the motor current.

I _BATT = (I _ARM x workload cycle) + (0A x (1-workload cycle))

I _BATT = I _ARM x Workload cycle

When using the above solid-state speed controller and using current 100A, voltage 18V, the difference is as follows.

V _ARM = 36 x workload cycle

18 = 36 x workload cycle

Workload cycle = 50%

I _BATT = I _ARM x Workload cycle

I _BATT = 100 A x 50%

I _BATT = 50A

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

P _BATT = I _BATT x V _BATT

P _BATT = 50 A X 36 V = 1800 watts

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

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

For example, when the vehicle moves down a hill, the normal operation of the motor armature winding 22 in the regenerative braking mode exists only when 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 counter electromotive force is equal to or less than the battery voltage, the energy generated by the motor 14 can not flow into the battery pack 18 because the battery voltage is too high. To overcome this limitation, a power MOSFET 34 is added with the above-described freewheeling diode 42. If the speed of the vehicle is slower than the basic speed, the battery pack 18 can not be charged for the reason as described above, and therefore the regenerative braking is not performed. To overcome this limitation, the mosfet 34 is simply turned on. When the MOSFET 34 is fully energized, the potential difference across its ends becomes substantially zero, so that the motor 14 generates a large current which is simply passed through the MOSFET 34 . Since this brief current can not be stopped immediately, a large voltage exceeding the normal counter electromotive force, i.e., the battery voltage, is generated. Next, the armature winding 22 pumps the energy into the battery pack 18 for the period of the briefing. The brief period is equal to the time required for the high voltage of the motor 14 to drop from the peak to the battery voltage. Next,

In order to cause the motor 14 to generate a voltage sufficiently high enough to generate a regenerative braking effect on both ends of the battery pack 18, the above process is repeated hundreds or thousands of times per second Is repeated. Thus, the motor 14 is gradually reduced in speed.

It is very important that strong braking is applied to the motor 14 by the mosfet 34 by turning on the mosfet 34. It is a common method for braking a direct current (DC) motor, but it is not desirable if the time is too long. It is therefore important to customize this braking operation in one or more ways. However, the characteristics of the power MOSFET 34 need to be turned on or turned off. Thus, in order to obtain a characteristic effect, it is necessary to change the cycle of the armature pulse width modulation work. Table 2 below provides values for the pulse width modulation duty cycle for V _BATT , I _BATT , I _ARM , and V _ARM .

% Work 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 operating mode. At this time, that is, when the series power MOSFET 36 is off and in the normal operation mode, the current continues to flow, and the armature voltage is reversed to push the current through the free wheel diode 42.

In the conventional electric golf car, the motor 14 causes regenerative braking to occur when the speed of the vehicle is 16 Km or more per hour. Regenerative braking does not occur when the speed is less than 16 km / h. The regenerative braking is also used to limit the downhill vehicle speed. To make it even safer, regenerative braking does not occur when the pressure on the accelerator pedal is relaxed, ie the vehicle speed is 20.8 km / h (13 miles per hour).

An important advantage of the present invention is that the accelerator pedal is used to decelerate the vehicle at a speed of at least two miles per hour. Previously known controllers limited the speed of the vehicle only when the pedal was fully released. That is, if the accelerator pedal is lightly depressed, the vehicle speed reaches the maximum speed of the motor 14, and the regenerative braking automatically stops at the maximum speed of the motor. This is undesirable especially where slopes are urgent. In the present invention, the accelerator pedal operates in the same manner as a vehicle having an internal combustion engine that performs a manual shift. That is, the accelerator pedal is used to directly adjust the low speed of the vehicle so as to establish 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) You can choose to place the pedals anywhere.

The maximum speed of the vehicle is a parameter determined by conventional controllers. This is the speed at which the vehicle gets at ground level. When the vehicle reaches the top of the hill and begins to descend the hill again, a typical conventional controller is set to limit its maximum speed, even as the vehicle is lowered on the hill and gravity acts to make the vehicle run faster.

In summary, in the conventional driving system, pedaling is simply used to accelerate the vehicle at the maximum speed at the base speed, and the motor can not be controlled at all below the basic speed. However, the position of the pedal in the system of the present invention allows the speed of the vehicle to be controlled from a speed near zero to a maximum speed set by the control system 16 and the motor 14 at any level. There may be a linear relationship between the position of the pedal and the vehicle speed. However, it can also be non-linear if desired. For example, in order to operate sensitively at a low speed, the counter electromotive force of the motor 14 increases with the speed of the motor and increases with the increase of the field winding current. In a dc 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 can not be independently controlled. The field winding currents shall always be the same. In the decentralized motor, the motor armature winding 22 and the field winding 24 are completely separate so that the currents can be adjusted separately between the two circuits. Therefore, in order to reduce the back electromotive force of the motor, it is necessary to reduce the field winding current. This allows the motor control designer more flexibility to get the desired motor characteristics.

Figure 2 is a typical field map. Field maps are widely used terms in industry to describe the relationship between armature current and field current in decentralized motors. Each motor has a specific area with the best performance in the field map. Operation in an area too far from this area can cause fatal damage to the motor.

In the upper right quadrant of the field map, the line 46 represents the performance of a dc motor having a field current that functions as an independently controlled armature current. In decentralized motor systems, the field current and armature current can be independently controlled and become a non-linear curve 56, as also shown in the upper right quadrant, as shown in FIG. This particular field map allows for better performance under conditions that can be programmed in conventional controllers. However, conventional control techniques using the freewheel diode 42 and the 1/4 bridge armature circuit do not provide control in the upper left quadrant of the field map. However, the present invention provides a technique that operates in the upper left quadrant of the field map, such as line 58.

In a decentralized motor system with a known 1/4 bridge controller. The armature current can be actually 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 sensor 44 may measure the armature current I _ARM at a negative quadrant of the field map (left quadrant). Next, in accordance with 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 thus other elements based on this information could not be controlled.

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 as 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 is actually controlling the average voltage, which makes it impossible to obtain or obtain the desired field current. The problem with the field winding is that the resistance varies with temperature. Thus, even if the applied voltage is the same, the field current varies depending on the 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 the like. The feedback system of FIG. 3 also considers other ancillary elements that may destabilize the desired I _f signal.

The advantage gained by 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 decentral direct current motors operate within the range of I _f to I _ARM conditions. If the motor 14 is operated for a long period of time in a condition outside the range, the motor 14 may be damaged. Therefore, the reliability and serviceability of the motor 14 can be controlled by downhill regeneration conditions or other abnormalities that may cause the motor 14 to exceed the normal operating range I _f / I _ARM In all cases involving environments, it is increased by guaranteeing the recommended I _f / I _ARM .

The problem in the regenerative safe driving area occurs when the vehicle is a large vehicle such as a five-seater golf car. This is because generally a small two-passenger golf car does not run long enough to adversely affect the motor 14 in the undesirable I _f / I _ARM region. In addition, on a hill or mountain course, the large vehicle tends to exert a high stress on the motor.

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

To obtain the desired motor speed, the voltage across the armature winding 22 must be adjusted. Control of the voltage across the armature terminal of the motor is accomplished by operation of power MOSFETs 34 and 36 for the armature winding 22. The MOSFETs operate in a preferred way to obtain the desired motor voltage. If the current speed of the vehicle that determines the speed of the motor 14 is given, the desired voltage or reverse power to be applied to the terminals of the motor may be calculated, and the power MOSFETs 34, Lt; RTI ID = 0.0 > of the < / RTI > Regenerative braking is induced by lowering the voltage of the motor armature terminal below the counter electromotive force. So that the voltage applied to the motor armature winding 22 is adjusted in a 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 the regenerative braking until the motor 14 reaches a basic speed, e.g., 16 km / h. Active control does not occur since the regenerative braking characteristic of the motor 14 can not provide a sufficient counter electromotive force exceeding the battery voltage. Therefore, it does not regenerate. 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. [

If during slow speed regenerative braking, the control system allows a linear relationship between the maximum I _ARN and speed, the vehicle speed decelerates very quickly when the pedal is released. Basically, this is similar to driving a car at a parking stop. Fundamentally, when the vehicle speed is higher than the speed indicated by the pedal position, the vehicle generally costs. In this improved system, if active regenerative braking is on, such regenerative braking will actually slow down the vehicle very quickly. These features also make regenerative braking below some setpoint low speed where the cost of starting the vehicle starts to go up. It is preferable that the critical low speed is between 12 km / h (8 miles per hour) and 3.2 km / h (8 km / h) and 8 km / h (5 miles per hour) in hilly areas.

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

As described above, the control system of the electric vehicle of the present invention has several advantages over the prior art. One of these advantages is the regenerative braking below the base speed. If the motor 14 is operating at or below its base speed, i.e. if its counter electromotive force is below the 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, the current flow in the counterclockwise direction starts at the point where the MOSFET 34 is turned off. As a result, a large voltage spike across the motor 14 occurs, resulting in a reverse current flow to the battery pack 18. Current flow can be maintained by rapidly turning on / off the mosfet 34 and regenerative braking can occur at lower speeds.

In addition, control of the negative quadrant of the field map is enabled because armature current is monitored. By changing I _f to fit I _REF , the field map curves are maintained. Also, since the motor speed varies with armature voltage V _ARM , the armature pulse width modulation can be used to control vehicle speed as opposed to the method of field current fluctuation speed control in previous controllers. Also through the closed control loop, the speed reference value (determined by the position of the pedal) is compared to the actual speed value sensed by the speed sensor. Adjustment of the armature pulse width modulation is made to vary the vehicle speed according to the throttle position input signal. And, to avoid sudden regenerative braking characteristics during low speed operation, the speed is monitored continuously and the regenerative armature current limit (I _MAX ) is reduced at low speed.

The foregoing discussion merely describes and discloses an embodiment of the present invention. Those skilled in the art will readily understand the present invention from the foregoing description and the appended drawings and claims, and that various changes, modifications, and variations will be apparent to those skilled in the art without departing from the scope and spirit of the claims of the invention Lt; / RTI >

Claims (28)

1. A control system for controlling a current and a voltage of an electric decentering motor associated with an electric vehicle, The motor includes an armature winding and a field winding, A plurality of switching elements electrically connected in the H-bridge circuit and electrically connected to the field winding; And Bridge circuit comprises a plurality of switching elements electrically connected in a half H-bridge circuit, wherein the switching elements in the half H-bridge circuit are arranged such that the first switching element is electrically connected in parallel with the armature winding and the second switching element Is connected in series to the armature winding, A control system for controlling the current and voltage of an electric decoupling motor associated with an electric vehicle. The control system according to claim 1, further comprising a freewheel diode electrically connected in parallel to the armature winding, wherein the control system controls the current and voltage of the decelerator motor associated with the electric vehicle. 3. The control system according to claim 2, wherein the freewheeling diode controls current and voltage of an electromotive decelerator motor associated with an electric vehicle formed as part of a MOSFET device which is a first switching device. The control system according to claim 1, wherein the plurality of switching elements in the H-bridge circuit and the half H-bridge circuit control current and voltage of an electromotive decelerator motor associated with an electric vehicle as a mosfet element. 2. The method of claim 1, further comprising: turning on and off the first switching element to control the armature current passing through the armature winding to provide regenerative braking of a low speed electric vehicle from a base speed to a speed zero And a control system for controlling the current and voltage of the decentration motor associated with the electric vehicle. 6. The control system according to claim 5, wherein said switching means comprises means for controlling the current and voltage of an electromotive decelerator motor associated with an electric vehicle including means for controlling an armature pulse width modulation signal to control the speed of the electric vehicle below its base speed Control system. 7. The apparatus of claim 6, wherein the means for controlling includes a pedal position device for determining an accelerator pedal position, a speed sensing device for determining a speed of the vehicle, and an armature pulse width modulation circuit for generating the armature pulse width modulated signal Wherein the pedal position device generates a speed reference signal, the speed sensing device generates a speed sensing signal, the speed sensing signal and the speed reference signal are applied to a summing junction, A control system for controlling a current and a voltage of an electromotive deceleration motor associated with an electric vehicle that generates a speed signal applied to an armature control circuit. The control system according to claim 6, wherein the pulse width modulation signal controls the current and voltage of the decentering motor associated with the electric vehicle applied to the second switching element. The control system according to claim 1, further comprising means for controlling the motor armature current between a minimum value and a maximum value as a function of speed, the current and voltage of the decelerator motor associated with the electric vehicle. 10. The method of claim 9, wherein the controlling means comprises a speed sensing circuit responsive to the speed sensing signal and having an additive junction responsive to a current sense signal from the current sensing circuit, the summing junction controlling the speed of the vehicle And a control system for controlling the current and voltage of the decentration motor associated with the electric vehicle generating the control speed detection signal for the electric deceleration motor. 2. The system of claim 1, further comprising means for measuring an armature current in a negative quadrant of the field winding map, the system comprising: means for selecting a field winding current for controlling field windings based on the measured armature current A control system for controlling the current and voltage of an electric decoupling motor associated with an electric vehicle. The apparatus of claim 1, further comprising means for generating field currents, the means for generating field currents including additive junctions responsive to and adding to the field currents and field current reference signals, And a field pulse width modulation circuit for generating a pulse width modulation signal from the electric motor. The control system according to claim 1, wherein the electric vehicle controls electric current and voltage of an electric decoupling motor associated with an electric vehicle that is an electric golf car. An electric golf car comprising a braking system, a battery system and a decentral motor, the motor comprising an armature winding and a field winding, The golf car, A plurality of MOSFETs electrically connected in the H-bridge circuit and electrically connected to the field windings; And In a plurality of MOSFETs electrically coupled in a half H-bridge circuit, a first MOSFET element is electrically connected in parallel with the armature winding and a second MOSFET is coupled in series with the armature winding Mosfetts of; A freewheel diode electrically connected in parallel to the armature winding; A current sensor for measuring an armature current passing through said armature winding; A speed pedal position switch for determining the position of the accelerator pedal of the golf car and generating a speed reference signal; And And a control system for switching on / off of the first MOSFET device to control the armature current flowing through the armature winding to provide regenerative braking at a speed of zero to zero at the golf car An electric golf car including a braking system, a battery system, and a decentralized motor 15. The system of claim 14, further comprising: an armature pulse width modulation circuit for generating an armature pulse width modulation signal; and a speed sensing circuit for determining a speed of the vehicle, wherein the pedal position switch determines a speed of the vehicle, Wherein the speed sensing circuit generates a speed sensing signal, the speed sensing signal and the speed reference signal are applied to an addition junction, and the summing junction generates a speed signal to be applied to the armature control circuit, Electric golf car including motor 16. The method of claim 15, wherein the pulse width modulation signal comprises a braking system applied to the second mosfet device, an electric golf car comprising a battery system and a decentralized motor 15. The system of claim 14, wherein the control system comprises a braking system comprising means for controlling motor armature current between a minimum value and a maximum value as a function of speed, an electric golf car comprising a battery system and a decoupling motor 15. The system of claim 14, wherein the control system comprises means for measuring an armature current in a negative quadrant of a field winding map, the control system selecting a field winding current for controlling a field winding based on the measured armature current , An electric golf car that includes a braking system, a battery system and a decentralized motor. 15. The apparatus of claim 14, wherein the control system includes means for generating field currents, the means for generating field currents comprise additive junctions responsive to and summing the field current and the field current reference signal, And a field pulse width modulation circuit for generating a pulse width modulation signal from the electric motor. Connecting the first switching element to the armature windings of the motor in parallel: And a limit for turning on and off the switching element to control an armature current passing through the armature winding to provide regenerative braking below the base speed of the motor. A method of controlling a speed of an electric vehicle including a motor. 21. The method of controlling a speed of an electric vehicle according to claim 20, wherein the step of electrically connecting the first switching device includes a MOSFET device electrically connected in parallel to the armature winding. 21. The method of claim 20, further comprising the step of electrically connecting the second switching element to the armature winding in series. 21. The method of controlling a speed of an electric vehicle according to claim 20, further comprising the step of controlling the vehicle speed between the base speed of the motor and the speed zero. 24. The method of claim 23, wherein controlling the vehicle speed below the base speed comprises: controlling a pulse width modulation signal applied to the armature winding; sensing a position of the accelerator pedal and a vehicle speed; Control method. 24. The method of claim 23, wherein controlling the vehicle speed comprises applying the pulse width modulated signal to a switching element in electrical series with the armature winding. 21. The method of claim 20, further comprising controlling motor armature current between a minimum value and a maximum value as a function of speed. 27. The method of claim 26, wherein controlling armature current comprises determining an armature current, determining a vehicle velocity, and combining the armature current with the vehicle velocity to control the velocity of the vehicle Control method. 21. The method of claim 20, further comprising: measuring an armature current in a negative quadrant of the field map winding; and controlling the field winding current based on the measured armature current.