Systems and methods for determining aspects of a state of a pantograph head

Abstract

The present disclosure relates to a systems and methods for determining aspects of a state of a pantograph head. The system may comprise: a pantograph having a pantograph head; one or more accelerometers mounted on the pantograph head; a camera configured to record images of the pantograph head; and a data processing system configured to determine information about the state of the pantograph head during operation, wherein the determination of at least one aspect of the state of the pantograph head comprises use of both of: (i) acceleration data obtained by the one or more accelerometers, and (ii) data obtained from the images recorded by the camera.

Description

SYSTEMS AND METHODS FOR DETERMINING ASPECTS OF A STATE OF A PANTOGRAPH HEADTECHNICAL FIELDSystems and methods for determining aspects of a state of a pantograph head.BACKGROUND

[0001] A pantograph is a device mounted on a roof of an electric locomotive to collect power (in the form of electric current) through contact with an overhead line. A pantograph typically comprises a pantograph head and a mechanism comprising one or more arms. The pantograph head is configured to contact the overhead line. The mechanism supports the pantograph head. The mechanism may be coupled to a roof of the electric locomotive, and configured such that the pantograph head can be lifted up and down.

[0002] While a locomotive is in motion, contact between the pantograph head and the overhead line should be consistent so that a motor of the electric locomotive can be provided with a reliable source of power. Thus, it is desirable that the dynamic interaction between the pantograph head and the overhead line can be accurately measured and monitored. European Standard EN 50317:2012 (Railway applications - Current collection systems - Requirements for and validation of measurement of the dynamic interaction on between pantograph and overhead contact line) specifies the functional requirements for the output and accuracy of measurements of the dynamic interaction between a pantograph and the overhead line for an electrified railway. In particular, it gives specification for: measuring the contact force between the pantograph and the overhead line; measuring the vertical position of the pantograph head; and detecting arcing, which occurs when there is a loss of contact between the pantograph and the overhead line.

[0003] Typically, it is difficult to implement sensors on a pantograph. This is because the overhead line is at a high voltage (e.g. around 25 kV), which means that a high current passes through the pantograph when the locomotive is in motion. Thus, providing systems for measuring the dynamic interaction between the pantograph head and the overhead line is difficult.

[0004] To measure the dynamic interaction between the pantograph and the overhead line, a system comprising a camera mounted on the roof of the electric locomotive has been proposed. The camera is directed at the pantograph. Images recorded by the camera are processed such that the vertical position of the pantograph head can be determined and tracked. The system utilises a state observer to obtain smoothed estimates of the vertical position of the pantograph head and the contact force between the pantograph head and the overhead line based on the vertical position of the pantograph head as determined from the images recorded by the camera. The state observer may utilise a linear dynamic model of the pantograph (e.g. a linear mass-spring-damper model).

[0005] Images recorded by the camera may also be processed to track a stagger of the pantograph and a tilt angle of the pantograph. The stagger of a pantograph is a lateral position (i.e. a position in a direction perpendicular to the overhead line) of the point of contact between the pantograph head and the overhead line. The tilt angle of the pantograph is an angle between the pantograph head and the horizontal (i.e. an angle about a longitudinal axis).

[0006] The system described above suffers from several disadvantages. For example, the measurement of the dynamic interaction between the pantograph head and the overhead line may be inaccurate and / or unreliable, as is described in further detail below.SUMMARY

[0007] The present disclosure is directed to providing a system for determining at least one aspect of the state of a pantograph head with improved accuracy and / or improved reliability.

[0008] According to an aspect of the present disclosure, there is a system. The system may comprise a pantograph having a pantograph head. The system may further comprise one or more accelerometers mounted on the pantograph head. The system may further comprise a camera configured to record images of the pantograph head. The system may further comprise a data processing system configured to determine information about the state of the pantograph head during operation. Determination of at least one aspect of the state of the pantograph head may comprise use of both of: (i) acceleration data obtained by the one or more accelerometers, and (ii) data obtained from the images recorded by the camera.

[0009] According to another aspect of the present disclosure, there is a method of determining information about the state of a pantograph head during operation. The methodmay comprise measuring vertical acceleration of the pantograph head. The method may further comprise recording images of the pantograph head. The method may further comprise determining information about the state of a pantograph head. Determining at least one aspect of the state of the pantograph head may comprise use of both of: (i) acceleration data obtained by the one or more accelerometers, and (ii) data obtained from the images recorded by the camera.

[0010] According to another aspect of the present disclosure, there is another method of determining information about the state of a pantograph head. The method may comprise receiving acceleration data for the pantograph head, and receiving images of the pantograph head or data obtained from images of the pantograph head. The method may further comprise determining at least one aspect of the information about the state of the pantograph head using both of (i) the acceleration data, and (ii) data obtained based on the images of the pantograph head.

[0011] The at least one aspect of the state of the pantograph head may be, for example, a contact force between the pantograph head and an overhead line; a vertical position of the pantograph head; a tilt angle of the pantograph head, optionally wherein the tilt angle is an angle in a frontal plane; and / or a torque applied to the pantograph head by an overhead line. By determining the at least one aspect of the state of the pantograph head based on acceleration data obtained by the one or more accelerometers and data obtained from the images recorded by the camera (e.g. rather than determining an aspect of the state of the pantograph head based only on data obtained from the images recorded by the camera), the dynamic interaction between the pantograph head and the overhead line can be measured more accurately and reliably. This is explained in further detail below.

[0012] According to another aspect of the present, there is a method of adapting one or more parameters of a dynamic model for a pantograph. The method may comprise measuring acceleration of the pantograph head. The method may further comprise recording images of the pantograph head. The method may further comprise adapting one or more parameters of the dynamic model based on: (i) the measured acceleration of the pantograph head, and (ii) data determined based on the recorded images.

[0013] According to another aspect of the present disclosure, there is provided another method of adapting one or more parameters of a dynamic model for a pantograph, wherein thepantograph comprises a pantograph head. The method may comprise receiving acceleration data for the pantograph head and receiving images of the pantograph head or data obtained from images of the pantograph head. The method may further comprise adapting one or more parameters of the dynamic model based on (i) the received acceleration data, and (ii) data obtained from the images of the pantograph head.

[0014] By adapting the one or more parameters (e.g. spring constants and / or damping coefficients) of the dynamic model based on the measured acceleration of the pantograph head and the data determined based on the recorded images, a more accurate dynamic model for the pantograph can be obtained. Moreover, by using the model adjustment method, it possible to update a dynamic model for a pantograph over the course of a lifetime of the pantograph, such that the dynamic model remain accurate (e.g. despite wear and damage to the pantograph which affects the dynamic response of the pantograph).BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which corresponding reference symbols indicate corresponding parts.Figure 1 depicts a typical pantograph.Figure 2 depicts an image processing system for determining the vertical position of the pantograph head.Figure 3 depicts a dynamic model of a pantograph.Figure 4 depicts a block diagram of a known pantograph measurement system.Figure 5 depicts a dynamic model of a pantograph, in accordance with an embodiment. Figure 6 depicts a block diagram of a pantograph measurement system according to the present disclosure.Figure 7 depicts a block diagram showing the structure of a Kalman filter / smoother which may be used in the pantograph measurement system according to the present disclosure.DETAILED DESCRIPTION

[0016] A typical pantograph 1 is depicted in Figure 1. The pantograph 1 comprises a pantograph head (“pantograph head”). The pantograph head 10 is the topmost part of the pantograph, designed to contact the overhead line. In use, the overhead line slides over the pantograph head 10. The pantograph head 10 is typically equipped with carbon strips to ensure good electrical conductivity and to reduce wear on the overhead line.

[0017] The pantograph 1 further comprises a mechanism. The mechanism may comprise an upper arm 12 and a lower arm 14. The upper arm 12 and the lower arm 14 may be coupled together at a hinged (i.e. rotatable) connection. The upper arm may be connected to the pantograph head 10. The lower arm 14 may be connected to a base frame 18 at a hinged (i.e. rotatable) connection. The base frame 18 is the foundation of the pantograph, and is configured to be mounted on a roof of a locomotive. The base frame 18 provides a stable base for the entire pantograph assembly, and houses the raising cylinder 16 and other components.

[0018] The pantograph 1 comprises a raising cylinder 16. The raising cylinder 16 may be responsible for lifting and lowering the pantograph. When activated, the raising cylinder 16 extends, pushing the lower arm 14 upwards.

[0019] The mechanism may further comprise a fourth bar 17. The fourth bar 17 may be coupled to the base frame 18 at a hinged (i.e. rotatable) connection and coupled to the upper arm 12 at a hinged (i.e. rotatable connection). The fourth bar 17 may be configured such that raising the lower arm 14 (relative to the body of the locomotive) also causes the upper arm 12 to be raised (relative to the lower arm 14).

[0020] The raising cylinder 16 may be hydraulic or pneumatic, for example. As depicted in Figure 1, the raising cylinder 16 is pneumatic, and the pantograph comprises air equipment 20 for supplying air to the raising cylinder 16. An air feed of the air equipment 20 may be insulated from a body of the locomotive by an air feed insulator 15.

[0021] When a locomotive is ready to draw power from an overhead line, the raising cylinder 16 is activated, and extends to cause the pantograph head 10 to be raised, such that the pantograph head 10 makes contact with the overhead line. The arms 14, 12 may be raised until a desired contact force is exerted between the pantograph head 10 and the overhead line. The contact force may mean that contact between the pantograph head 10 and the overhead line is maintained as the locomotive moves along the tracks.

[0022] The control rod / vane assembly 13 may be configured to maintain a desired force between the pantograph head 10 against the overhead line. However, the control rod / vane assembly 13 is not essential. The vane system is fixed, and is designed to compensate for different aerodynamic lifts associated with the pantograph 1. The control rod is connected to a pneumatic system, which is maintained at a constant pressure.

[0023] During use, electricity from the overhead line is conducted through the pantograph head 10 and down the arms 12, 14 to the electrical systems of the locomotive. The foot insulators 18 may ensure that the current does not pass into the body of the locomotive.

[0024] As the locomotive moves, the pantograph may adjust to variations in the height of the overhead line. For example, a height (i.e. a vertical position) of the pantograph head 10 may be adjusted in accordance with a changing distance between the tracks and the overhead line. The adjusting of the height of the pantograph head 10 may be passive. For instance, the raising cylinder 16 may be set at a fixed pressure, applying a constant force to the pantograph mechanism (e.g. to the lower arm 14). This constant force may cause the pantograph head 10 to move upward until the constant upward force from the raising cylinder 16 is balanced by the downward force exerted on the pantograph head 10 by the tension in the overhead line. In this sense, the control of height of the pantograph head is passive rather than active.

[0025] When the locomotive no longer needs to draw power, the raising cylinder 16 may be retracted, lowering the upper arm 12 and lower arm 14, and bringing the pantograph head 10 away from the overhead line.

[0026] A known system for measuring the dynamic interaction between the pantograph head and the overhead line will now be described. The system comprises a camera mounted on a roof of a locomotive, e.g. an electric locomotive. The camera may be directed at the pantograph head. Images recorded by the camera may be processed such that the vertical position of the pantograph head can be determined and tracked. An example of the processing performed to determine the vertical position of the pantograph head is depicted in Figure 2.

[0027] The system may utilise a state observer to obtain smoothed estimates of (a) the vertical position of the pantograph head, and (b) the contact force between the pantographhead and the overhead line. The state observer may use, as an input, the vertical position of the pantograph head as determined from the images recorded by the camera.

[0028] The state observer may utilise a linear dynamic model of the pantograph, e.g. a linear mass-spring-damper model. The linear dynamic model may be based on a linearised approximation of the dynamic response of the pantograph about an operating point that corresponds to the situation when the pantograph is raised, with the pantograph head 10 in contact with the overhead line with a given contact force. Figure 3 depicts an example of a mass-spring-damper model which may be utilised by the state observer. The mass-spring-damper model depicted in Figure 3 comprises three masses m1, m2, m3 arranged in series. A first mass m1 is coupled to a fixed reference via a first damper. The fixed reference is representative of the body of the locomotive on which the pantograph is mounted. A second mass m2 is connected to the first mass m1 via a second spring and second damper. A third mass m3 is connected to the second mass m2 via a third spring and a third damper. The position of the third mass m3 (i.e. x3(t)) is the vertical position of the pantograph head. The vertical position of the pantograph head may be referred to as the height of the pantograph head. The vertical position of the pantograph head may be measured relative to any suitable reference point, e.g. the roof of the locomotive. Each of the springs may have an associated spring constant. Each of the dampers may have an associated damping coefficient. The masses, springs and dampers are features of the linear dynamic model for the pantograph, and may not correspond to physical masses, dampers, springs in the pantograph mechanism.

[0029] In the dynamic model, a fixed force fo may be exerted on the first mass mi. The fixed force corresponds to the force exerted on the pantograph mechanism by the raising cylinder. A temporally-varying contact force / fz) is exerted on the third mass m3. The temporally-varying contact force / fz) may be the contact force exerted on the pantograph head by the overhead line.

[0030] Images recorded by the camera may also be processed to track a stagger of the pantograph. The stagger of a pantograph is a lateral position (i.e. a position in a direction perpendicular to the overhead line) of the point of contact between the pantograph head and the overhead line. An overhead line may extend along a zig-zag path relative to the path of the corresponding track. This may be such that the stagger (i.e. the lateral position of the point of contact) varies. This may improve a uniformity of the wear of the pantograph head.

[0031] Images recorded by the camera may also be processed to measure / monitor a tilt angle of the pantograph. The tilt angle of the pantograph may be an angle between the pantograph head and the horizontal (i.e. an angle about a longitudinal axis, i.e. an angle in the frontal plane).

[0032] Figure 4 depicts a block diagram of the known system. In Figure 4, y(t) is indicative of the height of the pantograph head (which is xs(t) in Figure 3). As shown in Figure 4, a state of the pantograph may be dependent on the contact force exerted on the pantograph head by the overhead line (i.e. f(t)), and the stagger (i.e. s(t)), which may be dependent on the arrangement of the overhead line. The state of the pantograph includes, for example: the height of the pantograph head y(t); the tilt angle of the pantograph head θ(t); and the stagger s(t).

[0033] In the known system, the measured / ob served variables of the state (i.e. the “aspects” of the state) of the pantograph may include: the height of the pantograph head ym(t); the tilt angle of the pantograph head θm(t) and the stagger sm(t). All of themeasured / ob served variables may be determined based on images recorded by the camera. The measured / ob served variables may be inaccurate / corrupted (e.g. may contain an error component) due to deficiencies / limitations of the camera. That is, the measured height of the pantograph head ym(t) may not equal the true height of the pantograph head y(t); the measured tilt angle of the pantograph head θm(t) may not equal the true tilt angle of the pantograph head θ(t); and the measured stagger sm(t) may not equal the true stagger s(t). In Figure 4, this error / inaccuracy in the measurements determined from the images recorded by the camera is represented by noise functions n1(t), n2(t), n3(t).

[0034] The measured height of the pantograph head;■"'( / ) may be input into the state observer. The measured tilt angle of the pantograph head 0m(t) and the measured stagger sm(f) may not be input into the state observer. As above, the state observer may utilise a dynamic model of the pantograph. The dynamic model may consider only the vertical dynamics of the pantograph. The dynamic model may be the dynamic model depicted in Figure 3.

[0035] The state observer may output an estimate of the vertical position of the pantograph head ŷ(t). The estimate of the vertical position of the pantograph head ŷ(t) may be improved, relative to the height of the pantograph head;■"'( / ) determined based on the images recorded by the camera. For example, the estimate of the vertical position of the pantographhead may be more accurate than the height of the pantograph head ym(t) determined based on the images recorded by the camera (e.g. because at least some of the error / inaccuracy introduced by the camera (i.e. noise function n1(t)) is removed and / or compensated for). The state observer may also output an estimate of the contact force between the pantograph head and the overhead line f(t).

[0036] The known system suffers from several disadvantages. First, the camera used in the system may be unable to detect small changes in the vertical position of the pantograph head. Consequently, the system may be unable to detect changes in the contact force between the pantograph head and the overhead line which are exerted alongside small changes in the vertical position of the pantograph head.

[0037] When the pantograph passes under a neutral section (or “section break”), which separates electrically isolated sections of the overhead line, a very large contact force may be exerted on the pantograph head for a short duration. The short duration may mean that the exertion of this very large force does not lead to a significant change in the vertical position of the pantograph head. Consequently, the large force exerted on the pantograph head when the pantograph passes under the neutral section may not be detected by the system.

[0038] Generally, because large forces with a short duration do not cause a detectable change in the position of the pantograph head, the known system may be limited to detecting variations in the contact force with a frequency of up to around 2 Hz. European Standard EN 50317:2012 requires that measurement systems should be able to detect variations in the contact force with a frequency of 20 Hz.

[0039] Second, in some circumstances, the system may be unable to determine the vertical position of the pantograph head from the images recorded by the camera. For example, during rapid changes in the light level around the locomotive (e.g. as the train enters a tunnel or emerges from a tunnel), the camera may record images from which the vertical position of the pantograph head cannot be determined (e.g. because the exposure settings of the camera have not been updated to the new light level, so the images recorded by the camera are underexposed or overexposed). Also, if a camera is not positioned correctly, the pantograph head may disappear from the field-of-view of the camera (e.g. at the top or bottom of the field-of-view) for some or all of the time in which the locomotive is in motion. Thus, there may be times during which the vertical position of the pantograph head and the contactforce cannot be obtained (or during which only an inaccurate approximation of the vertical position of the pantograph head and the contact force can be obtained).

[0040] Third, the state observer of the system may use a dynamic model of the pantograph which does not accurately reflect the dynamics of the pantograph. For example, the system may use a dynamic model of a standard pantograph or a standard type of pantograph, which differs from the actual pantograph that is being measured. Further, the state observer may use a dynamic model which is accurate for a newly-manufactured pantograph. The dynamics of a pantograph may change over the course of the lifetime of the pantograph (e.g. due to wear and / or damage). Thus, the dynamic model may not be accurate for a pantograph that has been in use for an extended period.

[0041] Fourth, the system may have a limited ability to detect points at which the pantograph head comes into and out of contact with the overhead line. This is because detecting the points at which the pantograph head comes into and out of contact with the overhead line is performed based on the images recorded by the camera, and the exact location of a contact point in three-dimensional space cannot be directly derived from a two-dimensional image. The system may attempt to detect the points at which the pantograph head comes into and out of contact with the overhead line by determining the tilt angle of the pantograph head from the images taken by the camera, and then determining the point at which the pantograph head comes into or out of contact where there is a significant change (e.g. a step change) in the tilt angle. However, this requires the detection of small changes in the tilt angle, which the camera may not be capable of.

[0042] The present disclosure provides an improved system and method for pantograph measurement / monitoring. The system may be referred to as a pantograph measurement / monitoring system. The system and method may utilise a camera and one or more accelerometers mounted on the pantograph head to obtain more accurate and / or more reliable measurements of the dynamic interaction between the pantograph head and the overhead line.

[0043] The system may comprise a pantograph having a pantograph head. The pantograph may be mounted on the body of a locomotive, e.g. an electric locomotive. The electric locomotive may be powered by electricity supplied from the overhead line via the pantograph head. It will be recognised that a measurement system configured to perform thetechniques described herein may or may not comprise the pantograph and the locomotive themselves.

[0044] The system may comprise one or more accelerometers mounted on the pantograph head. The one or more accelerometers may each be configured to obtain acceleration data. The acceleration data may be data relating to the acceleration of the pantograph head, at least in the vertical direction. Incorporating data from a (e.g. one) accelerometer may provide improve the accuracy and / or reliability and / or bandwidth of the measurement of the vertical position of the pantograph head and / or the contact force between the pantograph head and the overhead line. Providing a plurality of accelerometers on the pantograph head may allow further benefits to be realised, as will be described below.

[0045] The system may comprise a camera configured to record images of the pantograph head. The camera may be the same as, or similar to the camera of the known system described above. The camera may be mounted on the roof of the body of the locomotive. Alternatively, the camera may be mounted on a roof of a carriage that is adjacent to the locomotive. The camera may be directed at the pantograph head. The camera may be configured to record images, from which data (e.g. data pertaining to the vertical position of the pantograph head) can be determined.

[0046] The system may further comprise a data processing system. The data processing system may be configured to perform a determination process, comprising determining information about the state of the pantograph head during operation. Aspects of the state of the pantograph head may include: the contact force between the pantograph head and an overhead line; the vertical position of the pantograph head; the tilt angle of the pantograph head; and the torque applied to the pantograph head by an overhead line. The tilt angle may be an angle in a frontal plane (i.e. a plane substantially perpendicular to the direction of movement of the locomotive and / or substantially perpendicular to the direction in which the tracks propagate and / or substantially perpendicular to the direction in which the overhead line propagates).

[0047] The data processing system may be a computer system comprising one or more computers. The one or more computers may comprise one or more processors, including general purpose CPUs, graphical processing units (GPUs), tensor processing units (TPU) or other specialised processors. A computer used to implement the invention may be physical orvirtual. A computer used to implement the invention may be a server, a client or a workstation. Multiple computers used to implement the invention may be distributed and interconnected via a network such as a local area network (LAN) or wide area network (WAN). Some or all of the data processing system may be co-located with the pantograph. Some or all of the data processing system may be located remotely from the pantograph.

[0048] The receiving means may be in communication with the data processing system, such that data recorded by the one or more accelerometers and transmitted from the one or more transmitting means to the receiving means can be provided to the data processing system.

[0049] The determination of at least one aspect of the state of the pantograph head may comprise use of both of: (i) acceleration data obtained by the one or more accelerometers, and (ii) data obtained from the images recorded by the camera. By determining at least one aspect of the state of the pantograph head based on both the acceleration data obtained by the one or more accelerometers and the data obtained from the images recorded by the camera, the dynamic interaction between the pantograph head and the overhead line can be measured / monitored more accurately.

[0050] The determination of the at least one aspect of the state of the pantograph head may comprise fusion of the acceleration data obtained by the one or more accelerometer and the data obtained from the images recorded by the camera. In this context, sensor fusion refers to a process of combining data from, or data derived from, disparate sensor sources so that resulting information has less uncertainty than would be possible if these the disparate sensor sources were used individually.

[0051] The data processing system may be configured to perform an image analysis process. The image analysis process may comprise determining a vertical position of the pantograph head as a function of time based on the images recorded by the camera. Any suitable image recognition technique may be used in the image analysis process.

[0052] The data processing system may be configured to perform the determination process. As above, the determination process may be to determine information about the state of the pantograph head. For example, the determination process may be to determine the at least one aspect of the state of the pantograph head. The determination process may receive (as inputs) a vertical acceleration of the pantograph head obtained by the one or moreaccelerometers and a vertical position of the pantograph head determined based on the images recorded by the camera. By receiving two inputs which each relate to the movement of the pantograph head, the determination process may be able to provide an accurate, smoothed estimate of the vertical position of the pantograph head and / or the contact force between the pantograph head and the overhead line.

[0053] The determination process may comprise a state observer. The state observer may comprise a dynamic model of the pantograph, e.g. a linear mass-spring-damper model of the pantograph such as the mass-spring-damper model depicted in Figure 3. The state observer may be similar to the state observer described in relation to the known system. For example, the state observer may output an estimate of the vertical position of the pantograph head ŷ(t) and an estimate of the contact force f(t). Moreover, like in the known system, the state observer of the system of the present disclosure may receive, as an input, the height of the pantograph head (ym(t)) measured based on images recorded by the camera. The state observer of the system of the present disclosure differs from that of the known system in that the state observer also receives, as an input, a vertical acceleration of the pantograph head obtained by the one or more accelerometers. In the context of the mass-spring-damper model depicted in Figure 3, this means that the state observer receives, as inputs, x3(t) and ẍ3(t).

[0054] The state observer may be a Kalman smoother. Preferably, the Kalman smoother may be a fixed-lag Kalman smoother. The Kalman smoother may provide a delayed estimate of the vertical position of the pantograph head and / or the contact force between the pantograph head and the overhead line. That is, at a given time t, the Kalman smoother may provide an estimate of the vertical position of the pantograph head and / or the contact force between the pantograph head and the overhead line at time t-n, where n is the delay. The delay may be, for example, two seconds. Other known state observers may be used. For example, a Kalman filter may be used for the state observer.

[0055] A sample rate of the one or more accelerometers may be greater than a sample rate of the camera. Additionally or alternatively, the measurement of the height of the pantograph head based on the images recorded by the camera may be more accurate than the measurement of the acceleration of the pantograph head by the one or more accelerometers. By fusing the acceleration data obtained using the one or more accelerometers (which has a high sample rate) and the vertical position of the pantograph head obtained from imagesrecorded by the camera (which has a high accuracy, but a lower sample rate), the system of the present disclosure provides estimations of the vertical position of the pantograph head, and of the contact force between the pantograph head and the overhead line, that are accurate, and which include variations in the contact force with a higher frequency (e.g. up to 20 Hz or more). Consequently, the system may be able to detect variations in the contact force between the pantograph head and the overhead line arising when the variation in the contact force has a very short duration (e.g. when the pantograph passes a section break).

[0056] The one or more accelerometers may provide data pertaining to the vertical movement of the pantograph head when the position of the pantograph head cannot be obtained from the images recorded by the camera. Thus, the system of the present disclosure may provide improved estimates of the vertical position of the pantograph head and / or the contact force between the pantograph head and the overhead line when the locomotive is entering a tunnel or emerging from a tunnel (or in other circumstances in which the recognition of the vertical position of the pantograph head from the images recorded by the camera is compromised). Generally, the system of the present disclosure provides a more reliable and consistent estimate of the vertical position of the pantograph head and the contact force between the pantograph head and the overhead line (as compared to the known system, which considers only the information obtained from the camera).

[0057] The sample rate of the one or more accelerometers may be greater than 40 Hz, optionally greater than 50 Hz, and further optionally less than or equal to 100 Hz. The sample rate of the camera may be greater than 10 Hz, optionally greater than 15 Hz, less than 100 Hz, and optionally less than or equal to 50 Hz.

[0058] The system may comprise a plurality of accelerometers. The plurality of accelerometers may comprise a first accelerometer and a second accelerometer. The first accelerometer and the second accelerometer may be spaced apart from one another in the lateral direction. The first accelerometer may be a left accelerometer mounted on a left portion of the pantograph head. The second accelerometer may be a right accelerometer mounted on a right portion of the pantograph head.

[0059] From the accelerometer data obtained using the first accelerometer and the second accelerometer, information relating to the tilt angle of the pantograph head may be obtained. For example, the determination process performed by the data processing system may beconfigured to determine the tilt angle of the pantograph head based on vertical acceleration data obtained by the first accelerometer and vertical acceleration data obtained by the second accelerometer.

[0060] The determination of the tilt angle of the pantograph head may be based on a combination of the data from the first and second accelerometers and the images recorded by the camera (or data derived therefrom). For example, acceleration data from the first and second accelerometers may be fused with data obtained from the images recorded by the camera to provide an improved (e.g. more accurate and / or more sensitive) estimation of the tilt angle of the pantograph head. In other words, the tilt angle of the pantograph head may be determined based on: (a) the vertical acceleration data obtained by the first accelerometer, (b) the vertical acceleration data obtained by the second accelerometer, and (c) the images recorded by the camera.

[0061] Moreover, by combining the vertical acceleration data obtained using the one or more accelerometers with the tilt angle obtained from the images recorded by the camera, a torque applied to the pantograph head by the overhead line can be determined. From the torque applied to the pantograph head by the overhead line over time, times at which contact between the pantograph head and the overhead line is lost and made may be determined, e.g. by identifying times at which there is a large change in the torque applied to the pantograph head by the overhead line.

[0062] A method of determining information about the state of a pantograph head during operation may comprise use of the system described above. The method may comprise measuring the vertical acceleration of the pantograph head (e.g. using the one or more accelerometers). The method may further comprise recording images of the pantograph head (e.g. using the camera). The method may further comprise determining information about the state of a pantograph head, wherein determining at least one aspect of the state of the pantograph head comprises use of both of (i) the acceleration data (e.g. vertical acceleration data) obtained by the one or more accelerometers, and (ii) the data obtained from the images recorded by the camera. The determining of the at least one aspect of the state of the pantograph head may comprise fusing: (i) the acceleration data (e.g. vertical acceleration data) obtained by the one or more accelerometers, and (ii) the data obtained from the images recorded by the camera.

[0063] The method may comprise determining the vertical position of the pantograph head based on the recorded images, e.g. through image recognition. The determining of the at least one aspect of the state of the pantograph head may comprise fusing: (i) the acceleration data (e.g. vertical acceleration data) obtained by the one or more accelerometers, and (ii) vertical position of the pantograph head recognised from the images recorded by the camera.

[0064] The measuring of the vertical acceleration of the pantograph head (e.g. using the one or more accelerometers) and the recording of the images of the pantograph head (e.g. using the camera) may be performed while the pantograph head is in contact with an overhead line, and while the pantograph head is moving along the overhead line. For example, the measuring of the vertical acceleration of the pantograph head (e.g. using the one or more accelerometers) and the recording of the images of the pantograph head (e.g. using the camera) may be performed while the locomotive moves along a section of track below the overhead line.

[0065] A particular example of the system of the present disclosure will now be described with reference to Figures 5 and 6. The particular example comprises a plurality of advantageous features, some of which can be implemented independently (e.g. in the absence of other features described in relation to the particular example).

[0066] Figure 5 depicts a dynamic model of a pantograph which may be used in the system of the present disclosure. The dynamic model depicted in Figure 5 may be similar to that depicted in Figure 3, but additionally considers the tilt angle 0 f) of the pantograph head and the position at which the pantograph head contacts the overhead line (i.e. the stagger, s(fj). The dynamic model depicted in Figure 5 may comprise two springs and two dampers between the third mass m3 and the second mass m2. The two springs and two dampers are arranged in parallel. Providing two springs and two dampers in the dynamic modelling may facilitate the model of the tilt angle and related quantities (e.g. the torque applied to the pantograph head by the overhead line).

[0067] The dynamic model depicted in Figure 5 may additionally consider a movement (e.g. acceleration, ẍ0(t)) of the fixed reference to which the first mass m is connected via a damper. That is, the dynamic model depicted in Figure 5 may additionally consider the acceleration of the body of the locomotive on which the pantograph is mounted. Acceleration of the body of the locomotive may be measured by a body accelerometer mounted on thebody (e.g. on the roof) of the locomotive. The body accelerometer may be mounted close to (e.g. underneath) the pantograph. In some embodiments, the body accelerometer is mounted to an assembly which comprises the camera, e.g. the body accelerometer may be mounted to a camera housing. This may mean that all of the sensors required for the monitoring system of the present disclosure can be provided as a single package.

[0068] Figure 6 depicts a block diagram of the particular example of the system of the present disclosure. In Figure 6, ŷ(t) is indicative of the vertical position of the pantograph head (which is xs(t) in Figure 5). In Figure 6, yα(t) is indicative of a vertical acceleration, where α is indicative of the type of acceleration referred to.

[0069] As shown in Figure 6, a state of the pantograph may be dependent on the contact force exerted on the pantograph head by the overhead line (i.e. and the stagger (i.e. s(t)), which may be dependent on the arrangement of the overhead line.

[0070] From the camera, or images recorded thereby, the height of the pantograph head y(t); the tilt angle of the pantograph head θ*(t); and the stagger s(t) may be measured to provide measured signals pertaining to the height of the pantograph head ym(t); the tilt angle of the pantograph head ^“(Z); and the stagger sm(f). As explained above, error / inaccuracy in the measurements determined from the images recorded by the camera is represented by noise functionsn2(f),

[0071] A left accelerometer (e.g. an accelerometer mounted on a left side in the lateral direction of the pantograph head) may measure an acceleration of a left portion of the pantograph head yl(t) to provide a signal pertaining to the measured vertical acceleration of the left portion of the pantograph head ylm(t). A right accelerometer (e.g. an accelerometer mounted on a right side in the lateral direction of the pantograph head) may measure an acceleration of a right portion of the pantograph head yr(t) to provide a signal pertaining to the measured vertical acceleration of the right portion of the pantograph head y™(t). The body accelerometer may measure an acceleration of the body of the locomotive yb(t) to provide a signal pertaining to the measured vertical acceleration of the body of the locomotive ybm(t).

[0072] The measured / ob served accelerations may be inaccurate / corrupted (e.g. may contain an error component) due to deficiencies / limitations of the accelerometers. That is, the measured vertical acceleration of the left portion of the pantograph head y™(t) may not equalthe true acceleration of the left portion of the pantograph head yl(t); measured vertical acceleration of the right portion of the pantograph head y™(t) may not equal the true acceleration of a right portion of the pantograph head yr(t); and the measured vertical acceleration of the body of the locomotive y™(t) may not equal the true an acceleration of the body of the locomotive yb(t). In Figure 6, the error / inaccuracy in the measurements obtained by the accelerometers is represented by noise functions nl(t), nr(t), nb(t).

[0073] The measured height of the pantograph head ym(t) may be input into the state observer. The measured tilt angle of the pantograph head 0m(t) and the measured stagger sm(f) may also be input into the state observer. This may be so that the state observer is able to provide estimates of variables such as the tilt angle of the pantograph head 0(t) and the torque applied to the pantograph head by the overhead line f (t).

[0074] The measured vertical acceleration of the left portion of the pantograph head y™(t), the measured vertical acceleration of the right portion of the pantograph head yrm(t) and the measured vertical acceleration of the body of the locomotive y™(t) may be input into the state observer.

[0075] As explained above, the state observer may utilise a dynamic model of the pantograph (e.g. a linear mass-spring damper model). The dynamic model may consider only the vertical dynamics of the pantograph. The dynamic model may be the dynamic model depicted in Figure 5. The state observer may be, or may comprise, a Kalman filter or a Kalman smoother, as described above.

[0076] Figure 7 depicts a block diagram showing the structure of a Kalmanfilter / smoother which may be used in the state observer. As shown, within the state observer, states may be adjusted by comparing the output of the system (as measured using the camera and / or the accelerometers) with the output of the observer. Further details regarding Kalman filters and smoothers is provided in Linear estimation (2000) T Kailath, AH Sayed, B Hassibi, Prentice-Hall, the entirety of which is hereby incorporated by reference. Further details regarding Kalman filters are provided in Linear Optimal Control (1971) BDO Anderson, JB Moore. The entirety of Linear Optimal Control, and in particular the discussion regarding Fig. 8.4-4 (b) on page 181, is hereby incorporated by reference. Further details regarding Kalman smoothing are provided in Kalman Filtering and Neural Networks (2001) SimonHaykin. The entirety of Kalman Filtering and Neural Networks, and in particular the discussion in Section 1.5, hereby incorporated by reference.

[0077] In some embodiments, the state observer may be an input estimator, as described in Grigorios Gakis & Malcolm C. Smith (2024) A limit Kalman filter and smoother for systems with unknown inputs, International Journal of Control, 97:3, 532-542, DOI:10.1080 / 00207179.2022.2157752, the entirety of which is hereby incorporated by reference.

[0078] The state observer may output an estimate of the vertical position of the pantograph head y() and an estimate of the contact force (t) between the pantograph head and the overhead line. Additionally or alternatively, the state observer may output an estimate of the torque applied to the pantograph head by the overhead line f (t). Additionally or alternatively, the state observer may output an estimate of the tilt angle 0(t) of the pantograph head. Additionally or alternatively, the state observer may output an estimate of the stagger s(t). Additionally or alternatively, the state observer may output an estimate of the acceleration of the left portion of the pantograph head dj(t) and / or the right portion of the pantograph head dr(t).

[0079] As will be appreciated, not all of the features depicted in the block diagram of Figures 6 and 7 are required to achieve advantages relative to the known system. To provide a more accurate and / or more consistent estimation of the vertical acceleration of the pantograph head and / or the contact force between the pantograph head and the overhead line, the block diagram of Figure 3 may be adapted such that the state observer additionally receives a signal pertaining to the acceleration of the pantograph head as measured by an (e.g. one) accelerometer.

[0080] By providing the state observer with two acceleration signals (recorded by two accelerometers) for left and right portions of the pantograph head, and by providing the state observer with the tilt angle and stagger as determined based on images recorded by the camera, the state observer is able to output accurate estimates of the torque applied to the pantograph head by the overhead line f (t) and the tilt angle 0(t). However, providing the state observer with the two acceleration signals from the two accelerometers, and the tilt angle and stagger as determined based on images recorded by the camera, is not necessary to improve the accuracy and / or consistency of the estimations of the vertical position and contact force. Moreover, while providing the state observer with the acceleration signal from thebody accelerometer may improve the accuracy and / or consistency of the estimations provided by the state observer, it is not required for the accuracy and / or consistency of the estimations to be improved relative to the known system.

[0081] A model adjustment process / method will now be described. The model adjustment process may be performed using the system described above (in whole or in part). In particular, the model adjustment process may be performed by the data processing system of the system described above (in whole or in part). However, this is not essential, and the model adjustment process may be performed by some other system.

[0082] The model adjustment process may comprise adjusting one or more parameters of a dynamic model of the pantograph. The one or more parameters of the dynamic model that are adjusted in the model adjustment process may be, for example, one or more spring coefficients and / or one or more damping coefficients of a mass-spring-damper model which represents the pantograph. Such a model adjustment process may be possible from the combination of the vertical position of the pantograph head (e.g. from the camera) and the vertical acceleration of the pantograph head (e.g. from the one or more accelerometers).

[0083] The model adjustment process may comprise measuring acceleration of the pantograph head; recording images of the pantograph head; and adapting one or more parameters of the dynamic model based on: (i) the measured acceleration of the pantograph head, and (ii) data determined based on the recorded images.

[0084] The model adjustment process may receive, as an input, an effective mass of the dynamic model (e.g. an effective mass of the linear mass-spring-damper model). The effective mass of the dynamic model may be determined by raising the pantograph (e.g. using the raising cylinder) from rest, and tracking a rate of increase in the vertical position (e.g speed) of the pantograph up to the point at which the pantograph head comes into contact with the overhead line. The pantograph 1 is raised by the raising cylinder 16, which acts as a damper. Thus, the speed is proportional to the force, with the constant of proportionality being the effective mass. The force is known (e.g. because it is controlled), with the constant of proportionality being the effective mass. Consequently, the effective mass can be determined.

[0085] The reason for providing the model adjustment process with the effective mass of the dynamic model as an input is that, when estimating the parameters of the dynamic modelwhen the variance of force variations is unknown, it may only be possible to determine a scaling factor for the parameters. That is, the model adjustment process may allow the ratio between the parameters of the dynamic model to be determined, but not absolute values of the parameters of the dynamic model. The absolute values can be estimated based on the ratios between the parameters of the dynamic model and the effective mass of the system as determined from a separate process (e.g. as described above) is to estimate the effective mass of the system from a separate experiment - in this case, monitoring the rate (ie the speed) at which the pantograph rises before it is in contact with the overhead line. Because the system is raised by a cylinder, which acts as a damper, the speed is proportional to the force, which is known, with the constant of proportionality being the effective mass. The speed of the pantograph can be determined from the rate of change of the height of the pantograph, then knowing the force applied to the pantograph, the effective mass can be estimated.

[0086] The model adjustment process may take, as a starting point, a current version of a dynamic model. The current version of the dynamic model may be, for example, a standard dynamic model for a type of pantograph. The model adjustment method may comprise adapting one or more parameters of the dynamic model. The adapting of the one or more parameters may comprise iteratively changing the parameters. The adapting of the one or more parameters may utilise machine learning. Because the observer is based on a linear model of the dynamics, system identification methods (e.g. linear system identification methods) can be used to estimate a model of the dynamics. Details are given in Ljung, L. (1999) System Identification: Theory for the User. 2nd Edition, Prentice Hall PTR, Upper Saddle River, the entirety of which is hereby incorporated by reference. One approach is to use grey box estimation, as described in Bohlin, Torsten P. (7 September 2006). Practical Grey-box Process Identification: Theory and Applications. Springer Science & Business Media, the entirety of which is hereby incorporated by reference.

[0087] The output of the model adjustment process may be an adjusted dynamic model of the pantograph. The adjusted dynamic model of the pantograph may more accurately reflect the true dynamics of the pantograph than the standard dynamic model of the pantograph. The dynamics of a pantograph may change over the course of the lifetime of the pantograph (e.g. due to wear and / or damage). Thus, by performing the model adjustment process at differentsta ges in the lifetime of a pantograph, it can be ensured that the dynamic model remains accurate through the lifetime of the pantograph.

[0088] The adjusted dynamic model may be deployed in pantograph monitoring / measurement systems, such as the pantograph measurement system described herein. By using the adjusted dynamic model, measurement / monitoring of the state of the pantograph can be performed more accurately.

[0089] The model adjustment process may be integrated within a pantograph measurement / measurement system, such as the pantograph measurement / monitoring system of the present disclosure. The model adjustment process may be performed concurrently with the measurement / monitoring of the pantograph. That is, the dynamic model of the pantograph used in the pantograph measurement / monitoring system may be continuously updated while the pantograph is being measured / monitored by the pantograph measurement / monitoring system. Thus, it may be ensured that the dynamic model used by the pantograph measurement / monitoring system remains accurate throughout the operation of the pantograph measurement / monitoring system.

[0090] The model adjustment process may be used to determine parameters for a pantograph for which a standard dynamic model is not available and / or is not known. Thus, through use of the model adjustment process, pantograph measuring / monitoring of the type described herein may be possible for a wider variety of pantographs.

[0091] It may be the case that mounting the one or more accelerometers on the pantograph head changes the dynamics of the pantograph. For example, mounting the one or more accelerometers on the pantograph head may cause the dynamics of the pantograph to deviate from a standard dynamic model known for the relevant type of pantograph. The model adjustment process may be performed to adapt the standard dynamic model such that it is accurate for the pantograph with the accelerometers mounted thereon.

[0092] For the advantages of the methods of the present disclosure to be realised, it may not be necessary for the acceleration and the images to be actively recorded. Instead, the methods may be performed on data previously recorded.

[0093] For example, a method of determining information about the state of a pantograph head may comprise receiving acceleration data for the pantograph head; receiving images of the pantograph head or data obtained from images of the pantograph head; and determining atleast one aspect of the information about the state of the pantograph head using both of (i) the acceleration data, and (ii) data obtained based on the images of the pantograph head. Such a method may comprise receiving images of the pantograph head, and obtaining, based on the images of the pantograph head, vertical position data for the pantograph head as a function of time. The determining of the information about the state of the pantograph head comprises fusing (i) the acceleration data, and (ii) the vertical position data for the pantograph head obtained based on the images of the pantograph head.

[0094] Additionally, a method of adapting one or more parameters of a dynamic model for a pantograph may comprise: receiving acceleration data for the pantograph head; receiving images of the pantograph head or data obtained from images of the pantograph head; and adapting one or more parameters of the dynamic model based on (i) the received acceleration data, and (ii) data obtained from the images of the pantograph head. Such a model adjustment process may comprise receiving images of the pantograph head, and obtaining, determining vertical position data for the pantograph head as a function of time, based on the received images. The method of claim 30, wherein the information about the state of the pantograph head comprises fusing (i) the acceleration data, and (ii) the vertical position data for the pantograph head obtained based on the images of the pantograph head.

[0095] The methods of the present disclosure may be performed by computer systems comprising one or more computers. A computer used to implement the invention may comprise one or more processors, including general purpose CPUs, graphical processing units (GPUs), tensor processing units (TPU) or other specialised processors. A computer used to implement the invention may be physical or virtual. A computer used to implement the invention may be a server, a client or a workstation. Multiple computers used to implement the invention may be distributed and interconnected via a network such as a local area network (LAN) or wide area network (WAN). Individual steps of the method may be carried out by a computer system but not necessarily the same computer system. Results of a method of the invention may be displayed to a user or stored in any suitable storage medium. The present disclosure may be embodied in a non-transitory computer-readable storage medium that stores instructions to carry out a method of the invention. Any suitable programming language may be used to implement the invention. The present disclosure may be embodiedin a computer system comprising one or more processors and memory or storage storing instructions to carry out a method of the invention.

[0096] Aspects of the invention are described in the following numbered clauses.1. A system comprising:a pantograph having a pantograph head;one or more accelerometers mounted on the pantograph head;a camera configured to record images of the pantograph head; anda data processing system configured to determine information about the state of the pantograph head during operation,wherein the determination of at least one aspect of the state of the pantograph head comprises use of both of: (i) acceleration data obtained by the one or more accelerometers, and (ii) data obtained from the images recorded by the camera.2. The system of clause 1, wherein the determination of the at least one aspect of the state of the pantograph head comprises fusion of: (i) the acceleration data obtained by the one or more accelerometers, and (ii) the data obtained from the images recorded by the camera. 3. The system of clause 1 or 2, wherein the information about the state of the pantograph head comprises one or more of:a contact force between the pantograph head and an overhead line;a vertical position of the pantograph head;a tilt angle of the pantograph head, optionally wherein the tilt angle is an angle in a frontal plane; anda torque applied to the pantograph head by an overhead line.4. The system of any of clauses 1 to 3, wherein the data processing system is configured to perform an image analysis process, the image analysis process comprising determining a vertical position of the pantograph head as a function of time, based on the images recorded by the camera.5. The system of any of the preceding clauses, wherein the data processing system is configured to perform a determination process to determine the information about the state of the pantograph head, wherein the determination process receives, as inputs:a vertical acceleration of the pantograph head obtained by the one or more accelerometers; anda vertical position of the pantograph head determined based on the images recorded by the camera.6. The system of clause 5, wherein the determination process uses a dynamic model of the pantograph.7. The system of clause 6, wherein the dynamic model of the pantograph comprises a mass-spring-damper model, optionally wherein the mass-spring-damper model is a linear mass-spring-damper model.8. The system of any of the preceding clauses, wherein the data processing system is a state observer.9. The system of clause 8, wherein the state observer is a Kalman smoother, optionally wherein the Kalman smoother is a fixed-lag Kalman smoother.10. The system of any of the preceding clauses, wherein a sample rate(s) of the one or more accelerometers is greater than a sample rate of the camera.11. The system of clause 9, wherein:the sample rate of the one or more accelerometers is greater than 40 Hz, optionally greater than 50 Hz, and further optionally less than or equal to 100 Hz; and / orthe sample rate of the camera is greater than 10 Hz, optionally greater than 15 Hz, less than 100 Hz, and optionally less than or equal to 50 Hz.12. The system of any of clauses 3 to 11, wherein:the system comprises a first accelerometer and a second accelerometer spaced apart from one another in a lateral direction, wherein the lateral direction is in the frontal plane; and the determination process is configured to determine the tilt angle of the pantograph head based on vertical acceleration data obtained by the first accelerometer and vertical acceleration data obtained by the second accelerometer.13. The system of clause 12, wherein the determination process is configured to determine the tilt angle of the pantograph head may be determined based on: (a) the vertical acceleration data obtained by the first accelerometer, (b) the vertical acceleration data obtained by the second accelerometer, and (c) the images recorded by the camera.14. The system of any of the preceding clauses, further comprising a locomotive or carriage having a body, wherein the camera is mounted on the body.15. The system of clause 14, wherein the locomotive is an electric locomotive, optionally wherein the electric locomotive is powered by electricity supplied from the overhead line via the pantograph head.16. The system of any of clause 14 or 15, further comprising one or more body accelerometers mounted on the body, and the determination of the at least one aspect of the state of the pantograph head further comprises use of acceleration data measured by the one or more body accelerometers.17. The system of any of the preceding clauses, wherein the data processing system is configured to perform a model adjustment process to adjust one or more parameters of a dynamic model of the pantograph.18. The system of clause 17, wherein the one or more parameters comprises one or more spring coefficients and / or one or more damping coefficients.19. A method of determining information about the state of a pantograph head during operation, the method comprising:measuring vertical acceleration of the pantograph head;recording images of the pantograph head; anddetermining information about the state of a pantograph head, wherein determining at least one aspect of the state of the pantograph head comprises use of both of: (i) the measured vertical acceleration of the pantograph head, and (ii) the recorded images of the pantograph head.20. The system of clause 19, wherein the determining of the at least one aspect of the state of the pantograph head comprises fusing: (i) the measured vertical acceleration of the pantograph head, and (ii) the recorded images of the pantograph head.21. The method of clause 20, wherein the information about the state of the pantograph head comprises one or more of:a contact force between the pantograph head and an overhead line;a vertical position of the pantograph head;a tilt angle of the pantograph head, optionally wherein the tilt angle is an angle in a frontal plane; anda torque applied to the pantograph by an overhead line.22. The method of any of clauses clause 19 to 21, further comprising determining a vertical position of the pantograph head based on the recorded images.23. The method of any of clauses 19 to 22, wherein the determining of the the information about the state of the pantograph head comprises fusing (i) the measured vertical acceleration of the pantograph head, and (ii) the vertical position of the pantograph head determined based on the recorded images.24. The method of any of clauses 19 to 23 wherein the determining of the information about the state of the pantograph head comprises use of a Kalman smoother, optionally wherein the Kalman smoother is a fixed-lag Kalman smoother.25. The method of any of clauses 19 to 24, wherein the determining of the information about the state of the pantograph head comprises use of a dynamic model of the pantograph, optionally wherein the dynamic model is a mass-spring-damper model.26. The method of any of clauses 19 to 25, wherein at least the measuring of the vertical acceleration of the pantograph head and the recording of the images of the pantograph head are performed while the pantograph head is in contact with an overhead line, and while the pantograph head is moving along the overhead line.27. The method of clause 26, wherein:a pantograph comprises the pantograph head;the pantograph is mounted on a roof of a locomotive; andat least the measuring of the vertical acceleration of the pantograph head and the recording of the images of the pantograph head are performed while the locomotive moves along a section of track below the overhead line,optionally wherein the locomotive is powered by electricity supplied to the locomotive from the overhead line via the pantograph.28. The method of any of clauses 19 to 27, further comprising measuring an acceleration of a locomotive to which the pantograph is mounted, and wherein the determining of information about the state of a pantograph head further comprises use of the measured acceleration of the locomotive.29. A method of adapting one or more parameters of a dynamic model for a pantograph, the method comprising:measuring acceleration of the pantograph head;recording images of the pantograph head; andadapting one or more parameters of the dynamic model based on: (i) the measured acceleration of the pantograph head, and (ii) data determined based on the recorded images.30. A computer program comprising instructions to cause the data processing system of the system of any of clauses 1 to 18 to execute the method of any of clauses 19 to 29.31. A method of determining information about the state of a pantograph head, the method comprising:receiving acceleration data for the pantograph head;receiving images of the pantograph head or data obtained from images of the pantograph head; anddetermining at least one aspect of the information about the state of the pantograph head using both of (i) the acceleration data, and (ii) data obtained based on the images of the pantograph head.32. The method of clause 31, wherein the method comprises receiving images of the pantograph head, and obtaining, based on the images of the pantograph head, vertical position data for the pantograph head as a function of time.33. The method of clause 32, wherein the determining of the information about the state of the pantograph head comprises fusing (i) the acceleration data, and (ii) the vertical position data for the pantograph head obtained based on the images of the pantograph head.34. A method of adapting one or more parameters of a dynamic model for a pantograph, wherein the pantograph comprises a pantograph head, and the method comprises:receiving acceleration data for the pantograph head;receiving images of the pantograph head or data obtained from images of the pantograph head; andadapting one or more parameters of the dynamic model based on (i) the received acceleration data, and (ii) data obtained from the images of the pantograph head.35. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of any of clauses 31 to 34.

Claims

CLAIMS1. A system comprising:a pantograph having a pantograph head;one or more accelerometers mounted on the pantograph head;a camera configured to record images of the pantograph head; anda data processing system configured to determine information about the state of the pantograph head during operation,wherein the determination of at least one aspect of the state of the pantograph head comprises use of both of (i) acceleration data obtained by the one or more accelerometers, and (ii) data obtained from the images recorded by the camera.

2. The system of claim 1, wherein the determination of the at least one aspect of the state of the pantograph head comprises fusion of (i) the acceleration data obtained by the one or more accelerometers, and (ii) the data obtained from the images recorded by the camera.

3. The system of claim 1 or 2, wherein the information about the state of the pantograph head comprises one or more ofa contact force between the pantograph head and an overhead line;a vertical position of the pantograph head;a tilt angle of the pantograph head, optionally wherein the tilt angle is an angle in a frontal plane; anda torque applied to the pantograph head by an overhead line.

4. The system of any of claims 1 to 3, wherein the data processing system is configured to perform an image analysis process, the image analysis process comprising determining a vertical position of the pantograph head as a function of time, based on the images recorded by the camera.

5. The system of any of the preceding claims, wherein the data processing system is configured to perform a determination process to determine the information about the state of the pantograph head, wherein the determination process receives, as inputs:a vertical acceleration of the pantograph head obtained by the one or more accelerometers; anda vertical position of the pantograph head determined based on the images recorded by the camera.

6. The system of claim 5, wherein the determination process uses a dynamic model of the pantograph, optionally wherein the dynamic model of the pantograph comprises a mass-spring-damper model, optionally wherein the mass-spring-damper model is a linear mass-spring-damper model.

7. The system of any of the preceding claims, wherein the data processing system is a state observer, optionally wherein the state observer is a Kalman smoother, optionally wherein the Kalman smoother is a fixed-lag Kalman smoother.

8. The system of any of the preceding claims, wherein a sample rate(s) of the one or more accelerometers is greater than a sample rate of the camera, and optionally wherein:the sample rate of the one or more accelerometers is greater than 40 Hz, optionally greater than 50 Hz, and further optionally less than or equal to 100 Hz; and / orthe sample rate of the camera is greater than 10 Hz, optionally greater than 15 Hz, less than 100 Hz, and optionally less than or equal to 50 Hz.

9. The system of any of claims 3 to 8, wherein:the system comprises a first accelerometer and a second accelerometer spaced apart from one another in a lateral direction, wherein the lateral direction is in the frontal plane; and the determination process is configured to determine the tilt angle of the pantograph head based on vertical acceleration data obtained by the first accelerometer and vertical acceleration data obtained by the second accelerometer,optionally wherein the determination process is configured to determine the tilt angle of the pantograph head may be determined based on: (a) the vertical acceleration data obtained by the first accelerometer, (b) the vertical acceleration data obtained by the second accelerometer, and (c) the images recorded by the camera.

10. The system of any of the preceding claims, further comprising a locomotive or carriage having a body, wherein the camera is mounted on the body, optionally wherein the locomotive is an electric locomotive, further optionally wherein the electric locomotive is powered by electricity supplied from the overhead line via the pantograph head.

11. The system of claim 10, further comprising one or more body accelerometers mounted on the body, and the determination of the at least one aspect of the state of the pantograph head further comprises use of acceleration data measured by the one or more body accelerometers.

12. The system of any of the preceding claims, wherein the data processing system is configured to perform a model adjustment process to adjust one or more parameters of a dynamic model of the pantograph, optionally wherein the one or more parameters comprises one or more spring coefficients and / or one or more damping coefficients.

13. A method of determining information about the state of a pantograph head during operation, the method comprising:measuring vertical acceleration of the pantograph head;recording images of the pantograph head; anddetermining information about the state of a pantograph head, wherein determining at least one aspect of the state of the pantograph head comprises use of both of: (i) the measured vertical acceleration of the pantograph head, and (ii) the recorded images of the pantograph head.

14. The system of claim 13, wherein the determining of the at least one aspect of the state of the pantograph head comprises fusing: (i) the measured vertical acceleration of the pantograph head, and (ii) the recorded images of the pantograph head.

15. The method of claim 14, wherein the information about the state of the pantograph head comprises one or more of:a contact force between the pantograph head and an overhead line;a vertical position of the pantograph head;a tilt angle of the pantograph head, optionally wherein the tilt angle is an angle in a frontal plane; anda torque applied to the pantograph by an overhead line.

16. The method of any of claims 13 to 15, further comprising determining a vertical position of the pantograph head based on the recorded images.

17. The method of claim 15 or 16, wherein the determining of the information about the state of the pantograph head comprises fusing (i) the measured vertical acceleration of the pantograph head, and (ii) the vertical position of the pantograph head determined based on the recorded images.

18. The method of any of claims 15 to 17 wherein:the determining of the information about the state of the pantograph head comprises use of a Kalman smoother, optionally wherein the Kalman smoother is a fixed-lag Kalman smoother; and / orthe determining of the information about the state of the pantograph head comprises use of a dynamic model of the pantograph, optionally wherein the dynamic model is a mass-spring-damper model.

19. The method of any of claims 15 to 18, wherein at least the measuring of the vertical acceleration of the pantograph head and the recording of the images of the pantograph headare performed while the pantograph head is in contact with an overhead line, and while the pantograph head is moving along the overhead line,optionally, wherein:a pantograph comprises the pantograph head;the pantograph is mounted on a roof of a locomotive; andat least the measuring of the vertical acceleration of the pantograph head and the recording of the images of the pantograph head are performed while the locomotive moves along a section of track below the overhead line,further optionally wherein the locomotive is powered by electricity supplied to the locomotive from the overhead line via the pantograph.

20. The method of any of claims 13 to 19, further comprising measuring an acceleration of a locomotive to which the pantograph is mounted, and wherein the determining of information about the state of a pantograph head further comprises use of the measured acceleration of the locomotive.

21. A method of adapting one or more parameters of a dynamic model for a pantograph, the method comprising:measuring acceleration of the pantograph head;recording images of the pantograph head; andadapting one or more parameters of the dynamic model based on: (i) the measured acceleration of the pantograph head, and (ii) data determined based on the recorded images.

22. A method of determining information about the state of a pantograph head, the method comprising:receiving acceleration data for the pantograph head;receiving images of the pantograph head or data obtained from images of the pantograph head; anddetermining at least one aspect of the information about the state of the pantograph head using both of (i) the acceleration data, and (ii) data obtained based on the images of the pantograph head.

23. The method of claim 22, wherein:the method comprises receiving images of the pantograph head, and obtaining, based on the images of the pantograph head, vertical position data for the pantograph head as a function of time; and / orthe determining of the information about the state of the pantograph head comprises fusing (i) the acceleration data, and (ii) the vertical position data for the pantograph head obtained based on the images of the pantograph head.

24. A method of adapting one or more parameters of a dynamic model for a pantograph, wherein the pantograph comprises a pantograph head, and the method comprises:receiving acceleration data for the pantograph head;receiving images of the pantograph head or data obtained from images of the pantograph head; andadapting one or more parameters of the dynamic model based on (i) the received acceleration data, and (ii) data obtained from the images of the pantograph head.

25. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of any of claims 13 to 24.

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