Novelty detection with missing parameters
First Claim
1. A method of determining and displaying an index of novelty representing the state of a system based on measurements of a plurality of different parameters of the system, the system being a physical system or a biological system, the plurality of parameters defining respective dimensions of a multi-dimensional measurement space, the method being performed by a processor, and the method comprising the steps of:
- receiving sets of values each value in a set being a measurement of a different one of said plurality of parameters, each set defining a data point in said multi-dimensional measurement space;
calculating the index of novelty for each data point by comparing the position in said multi-dimensional measurement space of each data point to a set of prototype data points comprising measurements of said parameters representative of the system being in a normal state,wherein in the event of receipt of a deficient data point missing one or more of said parameter values of said set, the method further comprises the steps of;
calculating a marginal index of novelty of the deficient data point based on the position of the deficient data point in a reduced dimensionality space omitting the dimensions corresponding to the missing parameter values,using a predefined relationship, calculated for said reduced dimensionality space, between the marginal index of novelty and the marginal probability of different states of the system to find a marginal probability value representing the probability of the system being at least as close to said normal state as the state represented by the deficient data point,using a further predefined relationship, calculated for said multi-dimensional measurement space, between the index of novelty and the probability of different states of the system to find the index of novelty in said multi-dimensional measurement space corresponding to a probability equal to said marginal probability value; and
displaying the index of novelty so found as the index of novelty for the deficient data point.
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Accused Products
Abstract
A method of obtaining a consistent evaluation of the state of the system which has been monitored by measurement of multiple parameters of that system. The multiple parameters are used to calculate a single dimensional value based on the distance between the current state and normal states of the system using a Parzen Windows probability function. Consistent single dimensional values regardless of the dimensionality of the original data set can be obtained by finding a relationship between the single dimensional value and the probability of status of the system. Different relationships are obtained for different dimensionalities of data sets. Sensor malfunction can also be detected by testing the probability of the state implied by measuring all of the available parameters against the probability of the state implied by ignoring different individual ones of the parameters. A significant disparity in the two probabilities indicate possible sensor malfunction.
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Citations
30 Claims
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1. A method of determining and displaying an index of novelty representing the state of a system based on measurements of a plurality of different parameters of the system, the system being a physical system or a biological system, the plurality of parameters defining respective dimensions of a multi-dimensional measurement space, the method being performed by a processor, and the method comprising the steps of:
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receiving sets of values each value in a set being a measurement of a different one of said plurality of parameters, each set defining a data point in said multi-dimensional measurement space; calculating the index of novelty for each data point by comparing the position in said multi-dimensional measurement space of each data point to a set of prototype data points comprising measurements of said parameters representative of the system being in a normal state, wherein in the event of receipt of a deficient data point missing one or more of said parameter values of said set, the method further comprises the steps of; calculating a marginal index of novelty of the deficient data point based on the position of the deficient data point in a reduced dimensionality space omitting the dimensions corresponding to the missing parameter values, using a predefined relationship, calculated for said reduced dimensionality space, between the marginal index of novelty and the marginal probability of different states of the system to find a marginal probability value representing the probability of the system being at least as close to said normal state as the state represented by the deficient data point, using a further predefined relationship, calculated for said multi-dimensional measurement space, between the index of novelty and the probability of different states of the system to find the index of novelty in said multi-dimensional measurement space corresponding to a probability equal to said marginal probability value; and displaying the index of novelty so found as the index of novelty for the deficient data point. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 28, 29, 30)
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13. A method of determining and displaying an index of novelty representing the state of a system based on measurement of a plurality of different parameters of the system, the system being a physical system or a biological system, the method being performed by a processor, and the method comprising the steps of:
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receiving a data set comprising a plurality of sets of values each value being a measurement of a different one of said plurality of parameters, each set of values defining a data point in measurement space of dimension D, where D is a positive integer greater than one; calculating a provisional index of novelty for each data point by comparing the position in said measurement space of dimension D of each data point to a set of prototype data points comprising measurements of said parameters representative of the system being in a normal state; calculating a relationship, in said measurement space of dimension D, between the provisional index of novelty and the probability of different states of the system to find a probability value representing the probability of the system being at least as close to said normal state as the state represented by a data point having that provisional index of novelty, using said calculated relationship to find for each data point of the data set the probability value corresponding to its provisional index of novelty; using a further predefined relationship between the probability of different states of the system and an index of novelty defined in a space of dimension L, where L is a positive integer less than D, and based on comparing the distance between a data point and said normal state of the system, to find for each data point of the data set the index of novelty corresponding in the space of dimension L to said probability value; and displaying the index of novelty so found as the index of novelty for that data point. - View Dependent Claims (14, 15, 16, 17)
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18. A method of detecting sensor malfunction amongst a plurality of different sensors each measuring a parameter of the system, the plurality of parameters defining respective dimensions of a D-dimensional measurement space, where D is equal to the number of sensors, the method comprising the steps of:
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receiving sets of values, each value in a set being a measurement from a different one of said sensors, each set defining a data point in said D-dimensional measurement space; calculating an index of novelty for each data point by comparing its position in said D-dimensional measurement space to a set of prototype data points comprising measurements of said parameters representative of the system being in a normal state; using a predefined relationship, calculated for said D-dimensional measurement space, between the index of novelty and the probability of different states of the system to find a probability value representing the probability of the system being at least as close to said normal state as the state represented by the data point; calculating for each data point at least one marginal novelty index by ignoring one parameter value from said set of values and comparing the position of the data point in a D-1 dimensional space to the set of prototype data points also in the D-1 dimensional space, the D-1 dimensional space omitting the dimension corresponding to the ignored parameter; using a further predefined relationship, calculated for said D-1 dimensional space, between the marginal index of novelty and the marginal probability of different states of the system to find a marginal probability value representing the probability of the system being at least as close to said normal state as the state represented by the marginal novelty index; comparing said probability value and said marginal probability value; and in the event of the probability value and marginal probability value differing by more than a predefined threshold, outputting an alert for malfunction of the sensor whose parameter value was ignored. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification