Patent Description:
In aerospace applications, there may be one or more motors that are supplied to drive actuators within the aircraft, where the commutation of these motors is generally controlled by a control system. These motors are generally supplied with electrical power by a power converter that supplies electrical power. As will be understood by those skilled in the art, the power converter converts power from a source (such as a battery) to a form suitable for supply to the motor and other systems.

In order to control commutation of the motor, the position of the rotor must be 'known' by the control system, where the position information has traditionally been supplied by a sensors, such as Hall effect sensors.

Senseless (or 'sensorless') control systems exist in which voltage and/or current information from the motor can be used to determine information relating to the position of the rotor. Recent advancements in senseless control techniques allows for driving the salient permanent magnet (PM) motors over their full speed range without significant loss of torque. Such techniques provide for reduction in the cost of the electric machine, and may remove the harness required to carry either Hall effect or resolver signals, which are prone to noise interferences due to close proximity of the machine feeder cables.

Unfortunately, in many applications such as aerospace actuator applications, it is typically necessary to monitor the temperature of motor windings, e.g. using simple resistive temperature detectors (RTD). This monitoring requires a low voltage harness between the power converter and the motor in order to provide power to the sensors and to return data from the sensor that conveys the temperature signal from the sensor. This 'low voltage harness' between the motor and the converter can, in some applications, be up to <NUM> long. Those skilled in the art will appreciate that such a harness has a considerable physical volume and significant mass associated with it, which is highly undesirable for aerospace applications.

<CIT> discloses a device that can that can be attached to a structure or live subject and that can harvest energy from its environment to power sensing, storing and transmitting data about the structure or live subject.

<CIT> discloses an antenna, a microcontroller, and a power source. The power source is configured to generate power in response to ambient energy received at a first frequency during a cycle of energy harvesting using the antenna. The power is transferred to a power storage cell such that when the power storage cell has an amount of power the microcontroller of the device processes at least a part of a processing task to be sent to an end node, and a result of processing of said at least said part of the processing task is stored. During one or more additional cycles of energy harvesting, using generated power to process one or more additional parts of the processing task to assemble a payload or process a wireless transmission of the payload. The wireless transmission of the payload is sent over a second frequency to the end node.

In accordance with a first aspect, the present disclosure provides a sensor system for monitoring a motor in an aircraft, in accordance with claim <NUM>.

The first aspect of the disclosure also extends to a method of monitoring a motor in an aircraft, in accordance with claim <NUM>.

Thus it will be appreciated that examples of the present disclosure overcome the issues outlined above by powering a sensor using mechanical energy harvested from motion of the aircraft itself. As the wireless sensor can be powered locally by the energy harvesting unit, examples of the present disclosure may advantageously avoid the need for a wiring harness to carry power (e.g. from a main power converter of the aircraft to the sensor), which may be located remotely (e.g. of such a main power converter). Moreover, as the sensor is wireless, there may also be no need to provide a signal harness. Thus the present disclosure advantageously allows the benefits of senseless control of the aircraft's motor to be fully realised.

Those skilled in the art will appreciate that the term 'aircraft' as used herein extends to any vehicle that can fly, including but not limited to airplanes, helicopters, airships, blimps, and powered gliders.

Avoiding any wiring harness to the sensor that monitors the motor may also be beneficial due to a reduction in the weight and volume associated with the wiring harness that would have otherwise been required without the present disclosure. As outlined above, conventional wiring harnesses, known in the art per se, may be around <NUM> long, and be undesirably 'bulky'.

The present disclosure may be particularly advantageous for electric aircraft, i.e. aircraft that have fully electric (e.g. battery-powered) propulsion systems. The power source (e.g. a battery), may be located on the aircraft which is beneficial for weight-distribution purposes, while the wireless sensor can be provided proximate to the motor elsewhere on the aircraft without needing to run a wiring harness from that central power source location to the motor location.

The aircraft may comprise a power converter that drives the motor, where there is no electrical connection between the power converter that drives the motor and the wireless sensor. Such a power converter may source power from a suitable power source, e.g. a battery as outlined above or a 'conventional' aircraft engine such as a piston engine or gas turbine.

Additionally, avoiding the use of a wiring harness may advantageously help to avoid crosstalk noise between the sensor's interface signals and feeder cables.

The energy harvesting unit may be mechanically coupled to any part of the aircraft that exhibits motion, e.g. that vibrates. The energy harvesting unit is mechanically coupled to a component of the aircraft, and may be one of the following: a wing, a blade, a landing gear, or a flight control surface of the aircraft.

In some examples, the mass-spring arrangement has a resonant frequency substantially matched to a vibration frequency of the aircraft. Thus the method may, in some examples, further comprise determining the vibration frequency of the aircraft and substantially matching a vibration frequency of the mass-spring unit to the vibration frequency of the aircraft. It will be appreciated by those skilled in the art that the term 'vibration frequency of the aircraft' should be understood to mean a frequency of mechanical vibration that is known to exist within the aircraft.

It will be appreciated that there are a number of parameters of the motor that may be monitored with an appropriate sensor in accordance with examples of the present disclosure. However, in some examples, the wireless sensor comprises a temperature sensor, and optionally may comprise an RTD. Thus, in accordance with such examples, the parameter of the motor may comprise a temperature of the motor.

In some examples, multiple parameters of the motor may be monitored. A specific wireless sensor may itself monitor multiple different parameters, and/or the sensor system may comprise a plurality of wireless sensors, each arranged to monitor one or more parameters. Similarly, the aircraft may comprise a plurality of motors, wherein one or more wireless sensors may be provided to monitor some or all of these motors. In examples in which multiple parameters are monitored by one or more sensors, these may include parameters that are not necessarily parameters of the motor, for example a temperature elsewhere on the aircraft may be monitored, however in some examples multiple parameters of the motor may be monitored.

There are a number of mechanisms to convert the motion of the mass-spring unit to electrical energy, however in some examples, the energy harvesting unit may use magnetic, piezoelectric, and/or electrostatic methods. For ease of understanding only, the mass-spring arrangement may be seen as analogous to a 'tuning fork', where the motion of the aircraft, for example due to vibration from the motor or due to other causes of such vibration, gives rise to a vibration of the tuning fork (i.e. of the mass-spring unit).

With magnetic methods, the motion of the mass-spring unit causes a magnet to move relative to a coil. Thus the mass-spring unit may comprise a magnet that moves relative to a coil. Additionally or alternatively, the mass-spring unit may comprise a coil that moves relative to a magnet. As the magnet moves relative to the coil in response to the motion of the mass-spring unit, this induces an electrical current in the coil, thus providing the conversion of the mechanical energy of the aircraft to electrical energy for supply to the wireless sensor. Thus, in some examples, the mass-spring unit comprises a magnet and a coil, wherein motion of the mass spring unit moves the magnet relative to the coil, thereby generating the electrical energy.

The piezoelectric method, which may be used with some examples of the present disclosure, involves mechanically coupling the mass-spring unit to a piezoelectric element. Those skilled in the art will appreciate that a piezoelectric element is a device (typically a crystalline solid structure) that generates an electric charge in response to mechanical stress (e.g. when it is 'squeezed' or 'pressed'). Motion of the mass-spring unit causes a mechanical stress of the piezoelectric element, thereby generating an electrical charge that can be used to power the wireless sensor. Thus, in some examples, the mass-spring unit comprises a piezoelectric element, wherein motion of the mass spring unit applies a mechanical stress to the piezoelectric element, thereby generating the electrical energy.

The electrostatic method, used in accordance with some examples of the disclosure, makes use of a difference in electrostatic charge on the mass-spring unit compared to the electrostatic charge on a 'plate' proximate to the mass-spring unit. The mass-spring unit moves relative to a plate, where the varying distance or plate overlap causes a change in voltage, i.e. the arrangement behaves like a capacitor. Thus, in some examples, the mass-spring unit comprises first and second capacitive plates, wherein motion of the mass spring unit moves the capacitive plates relative to one another, thereby generating the electrical energy.

A combination of these different types of energy harvesting techniques may be used.

The wireless sensor transmits data to the external wireless receiver via a wireless communication interface. It will be appreciated that there are a number of wireless communication interfaces, known in the art per se, that could be used, including but not limited to Bluetooth®, Wi-Fi™, ZigBee®, or a proprietary wireless communication interface. The wireless communication interface can be selected depending on, for example, the wireless communication characteristics that are required (e.g. frequency, modulation scheme, range, power, noise performance, security, etc.).

It will be appreciated that the optional features described above in relation to examples of the first aspect of the disclosure apply equally as optional features of the second aspect of the disclosure.

Certain examples of the present disclosure will now be described with reference to the accompanying drawings, in which:.

<FIG> is a block diagram of a prior art motor drive system on an aircraft <NUM>. The aircraft <NUM>, which in this example is an airplane, has a fuselage portion <NUM> and a wing portion <NUM>. It will be appreciated that there are, of course, many other components to an aircraft, however these simplified 'portions' <NUM>, <NUM> are illustrated broadly for ease of reference.

In this particular example, the aircraft <NUM> is an electric aircraft, and is provided with a power converter <NUM> located at the centre of the fuselage portion <NUM>. This power converter <NUM> draws power from a battery <NUM> and converts the battery voltage to voltages suitable for supply to other systems of the aircraft <NUM>, including a motor <NUM>. In practice, there may be many motors on the aircraft <NUM>, however for ease of illustration, a single motor <NUM> is shown on the wing portion <NUM> of the aircraft <NUM>. The motor <NUM> is connected to the power converter via wiring harness <NUM>.

A temperature sensor <NUM> is provided on the motor <NUM> and is arranged to monitor the temperature of the motor <NUM> during use. This sensor <NUM> is connected to the power converter <NUM> via a wiring harness <NUM>, where this wiring harness is used to deliver electrical power from the power converter <NUM> to the temperature sensor <NUM>, and to return temperature data to a receiver <NUM> within the power converter <NUM>. The temperature data from the temperature sensor <NUM> may be used by the power converter <NUM> when determining the voltage and/or current supplied to the motor <NUM>.

Thus while the motor <NUM> may be driven by the power converter <NUM> without a feedback loop monitoring the motion of the motor <NUM>, i.e. in accordance with 'senseless control' principles, a wiring harness <NUM> is nonetheless required in order to supply power to, and receive data from, the temperature sensor <NUM>, preventing the prior art system from fully realising the benefits of senseless control.

<FIG> is a block diagram of a motor drive system on an aircraft <NUM> in accordance with an example of the present disclosure. Many of the components used in the aircraft <NUM> of <FIG> correspond to those in <FIG>, where reference numerals starting with a '<NUM>' in <FIG> correspond to those with reference numerals starting with a '<NUM>' in <FIG>.

Unlike in the aircraft <NUM> of <FIG>, the aircraft <NUM> of <FIG> is provided with an energy harvesting unit <NUM>, which is mechanically coupled to the wing portion <NUM> of the aircraft <NUM>. This energy harvesting unit <NUM> includes a mass-spring arrangement, where the mass is free to move on the spring in response to motion of the wing portion <NUM>. The mass-spring arrangement has a resonant frequency that corresponds to a natural (i.e. resonant) frequency of the wing portion <NUM>.

This energy harvesting unit <NUM> converts mechanical energy from the motion (e.g. vibration) of the wing portion <NUM> to electrical energy, and supplies this harvested electrical energy to the sensor unit <NUM>.

A further change from the aircraft <NUM> of <FIG> is that the sensor unit <NUM> in the aircraft <NUM> of <FIG> is wireless, i.e. it conveys the temperature data to the receiver <NUM> over a wireless communication interface <NUM>. The wireless communication interface <NUM> can be selected depending on, for example, the wireless communication characteristics that are required (e.g. frequency, modulation scheme, range, power, noise performance, security, etc.). It will be appreciated that there are a number of wireless communication interfaces, known in the art per se, that could be used, including but not limited to Bluetooth®, Wi-Fi™, ZigBee®, or a proprietary wireless communication interface. The present disclosure is not limited to any one particular interface.

This combination of the use of a wireless sensor unit <NUM> together with an energy harvesting unit <NUM>, located close to the wireless sensor unit <NUM>, removes the need for the wiring harness <NUM> used in the prior art aircraft <NUM>. This cuts down on the amount of weight associated with the wiring of the aircraft <NUM>, and results in more physical volume being free. The aircraft <NUM> of <FIG> may also suffer less crosstalk than the aircraft <NUM> of <FIG>.

<FIG> is a block diagram of the wireless sensor unit <NUM> used in the motor drive system of <FIG>. The wireless sensor unit <NUM> comprises a mass-spring unit <NUM>, where the mass-spring unit <NUM> includes a magnetic or piezoelectric transducer which converts mechanical energy from the vibrations of the aircraft <NUM> (in this case the wing portion <NUM>) to electrical energy (i.e. a voltage).

This electrical energy is then rectified and conditioned by electronic circuitry <NUM>. The rectified energy then is being used to power up the temperature sensor <NUM>, the measurements then being digitised by an analogue-to-digital converter (ADC) <NUM>. The digital data corresponding to the measured temperature of the motor <NUM> is then transmitted via a wireless transmitter <NUM> to the wireless receiver <NUM> in the main power converter <NUM>.

Claim 1:
A sensor system for monitoring a motor (<NUM>) in an aircraft (<NUM>), the sensor system comprising:
a wireless sensor (<NUM>) arranged to measure a parameter of the motor, said wireless sensor being further arranged to transmit said parameter to an external wireless receiver (<NUM>);
an energy harvesting unit (<NUM>) comprising a mass-spring unit (<NUM>) arranged to be mechanically coupled to the aircraft;
wherein the energy harvesting unit is arranged to convert mechanical energy arising from motion of the mass-spring unit to electrical energy using magnetic, piezoelectric, and/or electrostatic methods, and to supply said electrical energy to the wireless sensor;
characterised in that
the energy harvesting unit is arranged to be mechanically coupled to a component of the aircraft, wherein the component comprises one or more of the following: a wing; a blade; a landing gear; and/or a flight control surface of the aircraft.