Patent Description:
Trailers are a type of wheeled road vehicle that are pulled by another vehicle such as a tractor, as trailers do not have an engine for powering their own wheels for rotation. Trailers are common in the transportation industry, where the trailer is used to contain cargo, and a trailer may be connected to and disconnected from different tractors (also called trucks, lorry cars, or truck cars). The driver sits in the tractor and the tractor engine provides the motive power to pull the trailer to its destination.

Some trailers contain powered components, such as lights and/or refrigeration systems. The refrigeration system may be for cooling the cargo hold of the trailer, e.g. to preserve perishable goods such as foodstuffs or medicine. In some examples, the trailer receives all necessary electrical power from the tractor. That is, when the trailer is mounted to a given tractor, an electrical connection is also provided to provide power from the tractor battery or a generator in the tractor, to the trailer.

It is also known to provide a generator having a rotor connected to an axle of the trailer, such that, when the trailer is pulled by a tractor, the trailer wheels are driven to rotate and this rotation is passed, via the axle, to the rotor of a generator mounted on the trailer. The generator generates electrical power for use by the trailer.

Such conventional generators have generally been considered satisfactory for their intended purpose but there is room for improvement.

<CIT> discloses a selectively positionable power generating unit for recovering brake torque potential energy from an over-the-road vehicle. <CIT> discloses a vehicle drive control device and method. <CIT> discloses a refrigeration system including an electrical generator.

According to a first aspect, there is provided a generator system for connection to a vehicle axle. The generator system comprises: an electrically-actuated clutch having an engaged position and a disengaged position; a generator comprising: a rotor configured to be selectively connected, via the clutch, to the vehicle axle; and a stator; wherein, in the engaged position, the rotor is connected to the vehicle axle via the clutch such that torque from rotation of the vehicle axle is transmitted to the rotor, and wherein, in the disengaged position, torque from rotation of the vehicle axle is not transmitted to the rotor. A processor is provided and is configured to control the clutch to actuate between the engaged and disengaged positions; wherein the processor is configured to monitor an electrical output of the generator, wherein the processor is configured to command the clutch to move to the disengaged position if the electrical output moves outside a predetermined range. The generator system further comprises a sensor for detecting a rotational speed or frequency of the vehicle axle; wherein the sensor is connected to the processor, and wherein the processor is configured to: convert the detected rotational speed or frequency of the axle into an expected electrical output generated by the generator; determine a locked-state of the rotor if the monitored electrical output differs from the expected electrical output by more than a predetermined amount; and to control the clutch to move to the disengaged position in response to determining a locked-state of the rotor.

The electrical output may be one or more of electrical voltage, electrical current, or electrical frequency.

The predetermined range may be an electrical frequency range of from <NUM> to <NUM>; and/or the predetermined range may be an electrical voltage range of from <NUM> volts to <NUM> volts; and/or the predetermined range may be an electrical current range of from <NUM> amps to <NUM> amps.

<NUM> output may correspond to a maximum safe operational speed for the rotor, and so disconnecting the rotor if the output exceeds <NUM> may protect the generator. This may also protect any connected electronic components that are frequency sensitive.

<NUM> V may be a maximum rated output of the generator, and so disconnecting the rotor if the output exceeds <NUM> V may protect the generator and/or any connected electronic components.

<NUM> amps may be a maximum rated output of the generator, and so disconnecting the rotor if the output exceeds <NUM> amps may protect the generator and/or any connected electronic components.

Different generators may have a different maximum frequency output and/or different voltage output, and so the aforesaid maximum values of <NUM> and/or <NUM> V and/or <NUM> A may be reduced by configuring the processor as appropriate (e.g. the desired values for when the processor commands the clutch to disconnect may be set by software running on the processor).

Optionally, the minimum of the predetermined range may be <NUM> or <NUM> V or <NUM> A. In these cases, the processor may command the clutch to the disengaged position when the power output is non-zero but is insufficient for the necessary purposes. Necessary purposes may include powering a refrigeration system and/or charging a battery.

Similarly, a different minimum voltage or frequency or current may be set e.g. by software.

The expected electrical output may be an expected electrical frequency, or an expected electrical voltage, or an expected electrical current, as desired.

This may help protect a vehicle against unintended braking of the wheel(s) when the rotor is jammed (locked) within the generator. The predetermined amount allows for measurement errors in one or both of the sensed rotational speed and the detected electrical output of the generator. This helps avoid disconnecting the generator unnecessarily when everything is operating normally but a measurement error indicates a small discrepancy between the expected frequency and the detected frequency.

The processor may be further configured to: determine an overspeed state if the detected rotational speed or frequency of the axle is above a predetermined speed or frequency; and control the clutch to move to the disengaged position in response to determining an overspeed state.

This may protect the generator from being driven too fast, beyond its design parameters. This may also avoid letting the generator output too much power which could damage electronic components that are powered using the generator.

The generator system may further comprise a battery, wherein the battery is configured to supply electrical power to the electrically-actuated clutch and to the processor; and wherein the generator is configured to selectively provide power to the battery to charge the battery.

The battery may provide the power to engage/disengage the clutch to allow the generator system to be self-starting, i.e. in the case where the clutch is disengaged, the generator system has its own power to engage the clutch and thereby generate power from the generator.

The processor may be configured to detect a battery charge level and to control the clutch to move to the disengaged position in response to determining that the battery charge level is above a predetermined level.

In the case where the battery has low charge, it may be desirable to charge the battery using the generator, even if there is no other need for the generator power (e.g. if a refrigeration system is off etc.).

According to a second aspect, a trailer is provided, the trailer comprising: a wheel; an axle connected to the wheel; and the generator system of the first aspect. The rotor is selectively connected to the axle via the clutch; and wherein the axle is arranged to be driven in rotation by relative motion between the trailer and a surface the trailer is on.

The generator system may be used to provide electrical power to the trailer, e.g. to power lights or power a refrigeration system of the trailer. This can reduce or eliminate the need for electrical power to be provided to the trailer by a tractor pulling the trailer.

It is known that rotors may jam within a generator, for example due to friction between components of the generator. In known systems where the generator is permanently connected to the axle, this provides a braking force on the axle and thus on the trailer wheel(s). This can cause a safety risk from the wheels slipping against the road surface. Further, applying heavy torque from the wheels to a jammed rotor may damage the generator. Thus, being able to disconnect the generator from axle can improve safety for the trailer and improve the lifetime of the generator.

Additionally or alternatively, if the trailer is in motion but no electrical power is currently required from the generator, then the clutch may be disengaged to prevent the rotor unnecessarily spinning in the generator, thus reducing unnecessary wear on the generator components. Thus, being able to disconnect the generator from axle can improve the lifetime of the generator for this reason too.

The trailer may not have an engine for driving the axle. That is, the trailer may rely entirely upon a tractor to move the trailer from place to place. In this case, the generator system is connected to an axle that is freewheeling, i.e. not directly driven in rotation by a motor. Rather, the only cause of rotation of the wheel, and therefore of the generator, comes from the trailer being pulled over a road.

The trailer may further comprise a refrigeration system, wherein the generator system is connected to the refrigeration system and is arranged to selectively provide electrical power to the refrigeration system, under command of the processor.

The refrigeration system may therefore be powered by the generator, and this may reduce or eliminate the need for electrical power provided by the tractor. Alternatively or additionally, the refrigeration system may be powered by the battery and/or by a grid power supply.

The trailer may further comprise a communication link connected to the processor, wherein the processor is configured to provide information via the communication link regarding at least one of: the connection state of the electrically actuated clutch and the electrical output of the generator.

The communication link may provide information to a tractor computer or other screen. The communication link may provide information concerning one or more of: the electrical output of the generator, whether the generator is in a locked state, whether an overspeed state is occurring, whether a refrigeration system is powered on, etc..

According to a further aspect, there is provided a method of controlling a generator system, wherein a rotor of a generator of the generator system is arranged to be selectively connected to a vehicle axle via an electrically-actuated clutch such that, when the rotor is connected to the axle via the clutch, rotation of the vehicle axle drives the rotor to rotate within the generator. The method comprises: monitoring, using a processor, an electrical output of the generator; and disconnecting the rotor from the axle when the electrical output is outside a predetermined range. The method comprises: monitoring, using a sensor, a rotational speed of the vehicle axle; converting, using the processor, the rotational speed of the axle into an expected electrical output generated by the generator; determining, by the processor, a locked-state of the rotor when the monitored electrical output differs from the expected electrical output by more than a predetermined amount; and using the clutch, disconnecting the rotor from the axle in response to determining a locked-state of the rotor.

This method may protect the generator, e.g. from excessive wear when it is not required to generate power.

The predetermined range may be an electrical frequency range of from <NUM> to <NUM>; and/or the predetermined range may be an electrical voltage range of from <NUM> volts to <NUM> volts; and/or the predetermined range may be an electrical current range of from <NUM> amps to <NUM> amps. Alternatively, the minimum of each respective predetermined range may be <NUM> or <NUM> V or <NUM> A.

The method may comprise disconnecting the rotor from the axle if the rotational speed of the axle is above a predetermined rotational speed.

The method may comprise monitoring, using the processor, a charge level of a battery that is selectively electrically connected to the electrical output of the generator, and charging the battery using the electrical output of the generator, when the electrical output is above a predetermined threshold and when the charge level is below a predetermined threshold.

In this manner, the battery may be (re)charged when its charge gets too low, but can avoid overcharging the battery which can reduce battery lifetime or its ability to hold charge.

Certain embodiments of the present disclosure will now be described in greater detail by way of example only and with reference to the accompanying drawings in which:.

<FIG> shows a generator system <NUM> for generating electrical power from the rotation of a vehicle axle <NUM>. The generator system <NUM> comprises at least a generator <NUM>, an electrically-actuated clutch <NUM>, and a processor <NUM> configured to monitor an electrical output of the generator <NUM>.

The generator <NUM> is selectively connected to the axle <NUM> via the electrically-actuated clutch <NUM>. The generator <NUM> comprises a rotor 106a and a stator 106b. The clutch <NUM> has an engaged position in which rotation of the axle <NUM> is transmitted to the rotor 106a, to turn the rotor 106a relative to the stator 106b. The clutch <NUM> also has a disengaged position in which rotation of the axle <NUM> is not transmitted to the rotor 106a.

The generator <NUM> is electrically connected via an electrical line <NUM> to a control unit <NUM>. The control unit <NUM> houses the processor <NUM> and a battery <NUM>. The control unit <NUM> is electrically and communicatively connected to a refrigeration unit <NUM> and is configured to selectively provide electrical power to the refrigeration unit <NUM>. The connection between the refrigeration unit <NUM> and the control unit <NUM> may be via one or more electrical lines <NUM>.

The control unit <NUM> may also selectively connect to a grid power supply <NUM> via an electrical line <NUM>. The battery <NUM> may be charged from the grid power supply <NUM> when the control unit <NUM> is connected to the grid power supply <NUM>.

The battery <NUM> may be charged by electrical power from the generator <NUM>, e.g. when a battery charge level is below a predetermined level. The battery <NUM> provides electrical power to the processor <NUM>. This allows the processor <NUM> to function even when the generator <NUM> is not producing electrical power.

As shown in <FIG>, the vehicle axle <NUM> may be an axle of a trailer <NUM>. Trailers <NUM> are commonly used to transport goods and are pulled by a tractor <NUM> (also sometimes referred to as a truck). A given trailer <NUM> may be readily connected to and disconnected from different tractors <NUM>. The tractor <NUM> provides the motive power to pull the trailer <NUM>, and the trailer <NUM> typically has no engine or other means for turning its wheels. Instead, the trailer <NUM> relies entirely on tractors (e.g. tractor <NUM>) to move the trailer <NUM> from place to place.

The trailer <NUM> in <FIG> is a refrigerated trailer and has the refrigeration system <NUM>. The refrigeration system <NUM> is arranged to provide temperature control to the interior of the trailer, in order to keep goods stored therein at a predetermined temperature or within a predetermined temperature range. Operation of the refrigeration system <NUM> may be controlled, at least in part, by the processor <NUM> of the control unit <NUM>.

The control unit <NUM> is mounted to the trailer <NUM> and the generator <NUM> is mounted to or adjacent to the axle <NUM>. A communication link <NUM> is provided to communicatively connect the control unit <NUM> with a computer <NUM> on the tractor <NUM>. The computer <NUM> may provide information to a driver in the tractor <NUM>, e.g. to provide information on any of: the operation and/or performance of the refrigeration system <NUM>, the operation and/or performance of the generator <NUM>, the charge level of the battery <NUM>, and the position of the clutch <NUM> (i.e. engaged position vs disengaged position).

The communication link may <NUM> be a wired link or a wireless link.

When the trailer <NUM> is in motion on a road, e.g. due to being pulled by the tractor <NUM>, the wheels <NUM> of the trailer <NUM> are turned by friction with the road surface. One pair of the wheels <NUM> is connected to the axle <NUM> to which the generator <NUM> is selectively connected, via the clutch <NUM>. Thus, when the trailer <NUM> is in motion, the axle <NUM> rotates. This rotational motion may be transmitted to the generator <NUM>, via the clutch <NUM>, to generate electrical power from the rotational motion.

As mentioned above, the trailer <NUM> does not have its own engine. As such, neither the axle <NUM> nor the generator <NUM> are directly driven by an engine of the tractor <NUM>. Rather, the axle <NUM> is a free-wheeling axle that is turned by friction with a surface (e.g. road) over which the trailer <NUM> is being pulled by the tractor <NUM>. This axle <NUM> is therefore distinct from a driven axle of a vehicle that is mechanically connected to an engine such that rotation of an output shaft of the engine directly results in rotation of the wheels (i.e. regardless of any contact with a road).

<FIG> shows a schematic view of an exemplary axle <NUM> having the generator <NUM> mounted thereto.

The axle <NUM> has rotational end parts 150a,150b each for connecting to a wheel (e.g. wheel <NUM> shown in <FIG>) via connectors 152a,152b, respectively. The rotational end parts 150a,b are rotatable relative to a main axle shaft <NUM> that is connected to the trailer <NUM> via connection points 156a,156b. The main axle shaft <NUM> has a hollow interior and does not rotate relative to the trailer <NUM> when the trailer is in motion. A torque shaft <NUM> is connected at a first end to one of the rotational end parts 150a and extends within the hollow interior. The torque shaft <NUM> rotates along with rotation of the rotational end part 150a. A first gear 160a is attached to the torque shaft at or near a second end of the torque shaft <NUM>. The first gear 160a connects to a second gear 160b and the second gear 160b connects to a first side of the electrically-actuated clutch <NUM>. A generator shaft <NUM> extends from a second side of the electrically actuated clutch <NUM> and connects to the rotor 106a of the generator <NUM>. The first and second gears 106a,b may be selected to provide a fixed gear ratio as desired.

One or more bearings (not shown) may be provided to support some or all of the torque shaft <NUM>, generator shaft <NUM> and/or gears 160a,b within the main axle shaft <NUM>.

The generator <NUM> is fixed to the main axle shaft <NUM>. However, other arrangements are envisaged, such as connecting the generator to the trailer <NUM> rather than to the main axle shaft <NUM>.

With this arrangement, when the trailer <NUM> is pulled along a road by a tractor <NUM>, friction between the road and the wheel <NUM> causes the wheel <NUM> of the trailer <NUM> to rotate. With reference to <FIG> and <FIG>, rotation of the wheel <NUM> causes rotation of the rotational end part 150a of the axle, which in turn causes rotation of the torque shaft <NUM> and the gears 160a,b. If the clutch <NUM> is in the engaged position, rotation of the second gear 160b causes rotation of the generator shaft <NUM>, which turns the rotor 106a within the generator <NUM>. If the clutch <NUM> is in the disengaged position, the second gear 106b spins freely and rotation of this gear is not passed to the generator <NUM>.

The sensor <NUM>, if present, may be located at any point from the wheel <NUM> up to the first side of the clutch <NUM>.

Returning now to <FIG>, the processor <NUM> monitors an electrical output of the generator <NUM>. The term "electrical output" encompasses any one or more of electrical voltage, electrical frequency, and electrical current. That is, the processor <NUM> monitors: an output voltage from the generator, an output current from the generator, and/or an output electrical frequency from the generator.

The processor <NUM> also controls the electrically-actuated clutch <NUM> and may command the clutch <NUM> to actuate between the engaged and disengaged positions. The processor <NUM> is connected to the electrically-actuated clutch via a communication line <NUM>. This actuation of the clutch <NUM> may be accomplished using power from the battery <NUM>. As such, the clutch <NUM> may be moved between the engaged and disengaged positions even if the generator <NUM> is not currently producing electrical power or is producing an insufficient amount of electrical power. Alternatively, actuation of the clutch <NUM> may be performed using power from a grid power source <NUM>.

The processor <NUM> is configured to command the clutch <NUM> to move to the disengaged position if the electrical output moves outside a predetermined range. Examples of suitable predetermined ranges are disclosed below. Also discussed are specific situations that may lead to the electrical output moving outside the predetermined range.

The predetermined range may in some cases be multiple predetermined ranges, each predetermined range for a different electrical characteristic. For example, the processor <NUM> may monitor both electrical frequency and electrical voltage from the generator <NUM>, and may be configured to command the clutch <NUM> to move to the disengaged position if either the electrical voltage moves outside the predetermined range for voltage or if the electrical frequency moves outside the predetermined range for frequency.

A suitable predetermined range for electrical frequency may be, for example, <NUM> to <NUM>, and optionally <NUM> to <NUM>.

A suitable predetermined range for electrical voltage may be, for example, <NUM> V to <NUM> V, and optionally may be <NUM> V to <NUM> V, and optionally <NUM> V to <NUM> V.

A suitable predetermined range for electrical current may be, for example, from <NUM> A to <NUM> A, and optionally may be <NUM> A to 32A.

In some situations, the refrigeration system <NUM> is not required. For example, the trailer <NUM> may be being used to transport goods that do not require a temperature controlled environment, and thus the refrigeration system <NUM> may be turned off. In this case, the processor <NUM> may command the clutch <NUM> to move to the disengaged position so that the rotor 106a is not turned within the generator <NUM>. This may reduce wear on the generator <NUM> and extend its service life.

The refrigeration system <NUM> may require specific characteristics of received electrical power in order to function correctly, e.g. it may require specific voltage, electrical frequency, and/or electrical current. Similarly, the battery <NUM> may require specific characteristics of received power in order to recharge properly.

In some situations, the electrical output of the generator <NUM> may not be suitable for recharging the battery <NUM> and/or powering the refrigeration system <NUM>. For example, at low trailer <NUM> speeds, the generator <NUM> could produce electricity but this may have too low a frequency to meet the requirements of the refrigeration system <NUM> and/or battery <NUM>. In this case, the processor <NUM> may command the clutch <NUM> to move to the disengaged position so that the rotor 106a is not turned within the generator <NUM>.

The control unit <NUM> may contain power conversion electronics to convert the output from the generator <NUM> to electrical power having different characteristics. For example, the control unit may have power control electronics suitable for increasing or decreasing the voltage received from the generator, and/or for converting an A. output from the generator to D. power etc. However, the power control electronics may nonetheless require the power received from the generator <NUM> to have certain minimum or maximum characteristics (e.g. a minimum voltage, a maximum voltage, a minimum frequency, a maximum frequency, a minimum current, and/or a maximum current) in order to successfully produce output power that had the characteristics required by the refrigeration system <NUM> and/or battery <NUM>. If the electrical output is outside this range, i.e. such that the power conversion electronics cannot convert the electrical output to a suitable electrical supply for the refrigeration system <NUM> and/or battery <NUM>, then the processor <NUM> may command the clutch <NUM> to move to the disengaged position so that the rotor 106a is not turned within the generator <NUM>. This may occur, for example, if the trailer <NUM> is moving too slowly such that insufficient power is generated by the generator <NUM>. The battery <NUM> may be used to power the refrigeration system <NUM> instead, if required. Once the electrical output is within the predetermined range (e.g. if the trailer <NUM> speeds up), the processor <NUM> may command the clutch <NUM> to move to the engaged position so that the rotor 106a turns within the generator <NUM> and the generator <NUM> generates electrical power, e.g. for provision to the refrigeration system <NUM> and/or to recharge the battery <NUM>. A similar situation may prevail if the trailer <NUM> is moving too fast, such that e.g. an electrical frequency of the power generated by the generator <NUM> is too high, i.e. above the predetermined range.

In this situation, the predetermined range for the electrical output of the generator <NUM> may be one of: a minimum and maximum voltage, a minimum and maximum frequency, and a minimum and maximum current. Specific values for these minima and maxima will depend upon the specific requirements of the refrigeration system <NUM>, and/or battery <NUM>, and/or power conversion electronics.

One known type of malfunction of a generator (e.g. generator <NUM>) is the rotor locking within the generator <NUM>. Rotor locking may be caused, for example, by debris, failure of bearings in the generator <NUM>, or thermal expansion/contraction of parts of the generator <NUM>. In this situation, if the generator <NUM> is connected to the axle <NUM>, the generator <NUM> will act as a brake on the axle <NUM>. This unintentional braking of the axle <NUM> can be a safety risk, as it could cause the trailer <NUM> to slip on the road, or lead to loss of control of the trailer <NUM> and tractor <NUM>, which may lead to an accident.

A sensor <NUM> may be arranged to sense a rotational speed and/or rotational frequency of the axle <NUM>, e.g. as shown in <FIG>. Data from the sensor <NUM> is communicated, via a communication link <NUM>, to the processor <NUM>. The processor <NUM> may convert the rotational speed or frequency of the axle <NUM> into an expected electrical output of the generator <NUM>. The conversion of the rotational speed of the axle <NUM> to an expected electrical output will depend upon several factors, including: the arrangement of the generator, particularly the number of poles in the generator <NUM>, as well as any gears (e.g. gears 160a, b) between the wheel <NUM> and the rotor 106a.

If the electrical frequency output by the generator <NUM> deviates from the expected electrical output by more than a predetermined amount, this may indicate that the rotor 106a is stuck within the generator <NUM>. The predetermined amount is to allow for measurement error in either or both of: the electrical output of the generator <NUM> and the rotational speed measured by the sensor <NUM>. The predetermined amount may be, for example, +/- <NUM>.

In a similar manner, an expected voltage output or an expected current output may be calculated. The expected voltage output or expected current output may be compared to the electrical output of the generator <NUM> monitored by the processor and, if the monitored output deviates from the expected output by more than a predetermined amount, this may indicate the rotor 106a is stuck within the generator <NUM>. The predetermined amount may be, for example, +/- 5V or +/- <NUM> A, as appropriate.

In this scenario, the processor <NUM> may determine a locked-state of the rotor 106a and command the clutch <NUM> to move to the disengaged position so that the generator <NUM> does not brake the axle <NUM>.

By way of example only, if the sensor <NUM> detects the axle <NUM> is rotating at <NUM> (<NUM> rpm - which might typically correspond to a vehicle speed of <NUM> per hour), and the generator is a three pole generator then the processor <NUM> would calculate an expected electrical output frequency of <NUM>. If the processor detects an electrical output frequency of <NUM>, then it may determine that the generator <NUM> is operating normally, within measurement error. However, if the processor detects an electrical output frequency of <NUM>, this may indicate that the rotor 106a is partially sticking within the generator <NUM> and this sticking will be providing a unintended braking force on the axle <NUM>. In this case, the processor <NUM> may command the clutch <NUM> to move to the disengaged position so that the generator <NUM> does not brake the axle <NUM>.

If the rotational speed measured by the sensor <NUM> exceeds a predetermined maximum speed, the processor may determine an overspeed state. That is, the trailer <NUM> may be moving faster along a road than may be safely accommodated by the generator <NUM>. In this case, the processor <NUM> may command the clutch <NUM> to move to the disengaged position so that the generator <NUM> is not run faster than its design parameters. The predetermined maximum speed may alternatively be set based on requirements of the refrigerating system <NUM>, battery <NUM>, and/or power conversion electronics.

In a situation where the battery <NUM> charge is low, the processor may detect this low charge and command the clutch <NUM> to move to the engaged position so that the generator <NUM> provides power and this power is used to charge the battery <NUM>. This may occur, for example, even if the generator <NUM> is not otherwise required at present, e.g. not required to power the refrigeration system <NUM>.

In this situation, the processor may also be configured to control the clutch <NUM> to move to the disengaged position in response to determining that the battery charge level is above a predetermined level.

Claim 1:
A generator system (<NUM>) for connection to a vehicle axle (<NUM>); the generator system comprising:
an electrically-actuated clutch (<NUM>) having an engaged position and a disengaged position;
a generator (<NUM>) comprising:
a rotor (106a) configured to be selectively connected, via the clutch, to the vehicle axle; and
a stator (106b);
wherein, in the engaged position, the rotor is connected to the vehicle axle via the clutch such that torque from rotation of the vehicle axle is transmitted to the rotor, and
wherein, in the disengaged position, torque from rotation of the vehicle axle is not transmitted to the rotor; and
a processor (<NUM>) configured to control the clutch to actuate between the engaged and disengaged positions;
characterised by:
a sensor (<NUM>) for detecting a rotational speed or frequency of the vehicle axle; wherein the sensor is connected to the processor (<NUM>);
wherein the processor is configured to monitor an electrical output of the generator, wherein the processor is configured to command the clutch to move to the disengaged position if the electrical output moves outside a predetermined range; and wherein the processor is configured to:
convert the detected rotational speed or frequency of the axle into an expected electrical output generated by the generator;
determine a locked-state of the rotor if the monitored electrical output differs from the expected electrical output by more than a predetermined amount; and to
control the clutch (<NUM>) to move to the disengaged position in response to determining a locked-state of the rotor.