# US 12,594,924 B2 · Vehicle brake-by-wire diagnostic system and method

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- Number: US 12,594,924 B2
- Document ID: US12594924B2
- Status: Granted
- Kind: B2
- Application number: 18/653,181
- Filed: 2024-05-02
- Published: 2025-11-06
- Granted: 2026-04-07
- Earliest claimed: 2024-05-02
- Assignees: GM Global Technology Operations LLC
- Applicants: GM Global Technology Operations LLC
- Inventors: Hessam Kalbasi; Mohammad Karimi; SeyedAlireza Kasaiezadeh Mahabadi
- Web page: https://patentgrep.com/patent/US12594924B2

## CPC

- B60T 17/22: Devices for monitoring or checking brake systems; Signal devices
- B60T 17/221: {Procedure or apparatus for checking or keeping in a correct functioning condition of brake systems (hydraulic pressure systems in general F15B19/00, F15B21/04; testing structures or apparatus G01M)}
- B60T 2270/406: Test-mode; Self-diagnosis
- B60T: VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL (electrodynamic brake systems for vehicle, in general B60L; brakes per se, i.e. devices where braking effect occurs, including ultimate brake actuators, F16D); ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES

## Abstract

A method for diagnostic monitoring of a vehicle brake-by-wire system for a vehicle may include recording a reference excitation profile of a reference brake-by-wire unit. The method further may include identifying one or more characteristic functions of the reference brake-by-wire unit based at least in part on the reference excitation profile. The method further may include determining a performance of a vehicle brake-by-wire unit based at least in part on the one or more characteristic functions. The method further may include performing a diagnostic action based at least in part on the performance of the vehicle brake-by-wire unit.

## Claims

### Claim 1

A method for diagnostic monitoring of a vehicle brake-by-wire system for a vehicle, the method comprising:
recording a reference excitation profile of a reference brake-by-wire unit, wherein recording the reference excitation profile of the reference brake-by-wire unit further comprises:
recording the reference excitation profile of the reference brake-by-wire unit, wherein the reference brake-by-wire unit is a known healthy brake-by-wire unit, and wherein the reference excitation profile includes a requested clamp force versus time, a corresponding requested actuator displacement versus time, and a measured clamp force versus time;
identifying one or more characteristic functions of the reference brake-by-wire unit based at least in part on the reference excitation profile;
determining a performance of a vehicle brake-by-wire unit based at least in part on the one or more characteristic functions;
performing a diagnostic action based at least in part on the performance of the vehicle brake-by-wire unit; and
adjusting a maximum speed of the vehicle based at least in part on the diagnostic action.

### Claim 2 (depends on 1)

The method of claim 1, wherein identifying the one or more characteristic functions further comprises:
determining an end-to-end characteristic transfer function based at least in part on the requested clamp force versus time and the measured clamp force versus time; and
determining a mechanical characteristic function based at least in part on the requested actuator displacement versus time and the measured clamp force versus time.

### Claim 3 (depends on 2)

The method of claim 2, wherein determining the end-to-end characteristic transfer function further comprises:
determining a general form of the end-to-end characteristic transfer function, wherein the general form of the end-to-end characteristic transfer function models nominal overall system dynamics of the vehicle brake-by-wire unit, and wherein the general form of the end-to-end characteristic transfer function is characterized by a plurality of end-to-end system parameters; and
estimating a value for each of the plurality of end-to-end system parameters based at least in part on the requested clamp force versus time and the measured clamp force versus time.

### Claim 4 (depends on 3)

The method of claim 3, wherein determining the general form of the end-to-end characteristic transfer function further comprises:
determining the general form of the end-to-end characteristic transfer function to be a rational fractional polynomial:
H
end
-
end
=
b
0
⁢
s
m
+
b
1
⁢
s
m
-
1
+
⋯
+
b
m
s
n
+
a
1
⁢
s
n
-
1
+
⋯
⁢
a
n
·
e
-
T
d
⁢
s
wherein Hend-end is the end-to-end characteristic transfer function, s is a complex frequency variable, and the m, n, b, a, and Td factors are the plurality of end-to-end system parameters.

### Claim 5 (depends on 3)

The method of claim 3, wherein estimating the value for each of the plurality of end-to-end system parameters further comprises:
estimating a preliminary value for each of the plurality of end-to-end system parameters using a least-squares regression based at least in part on the requested clamp force versus time and the measured clamp force versus time; and
estimating the value for each of the plurality of end-to-end system parameters using a nonlinear optimization based at least in part on the preliminary value for each of the plurality of end-to-end system parameters, the requested clamp force versus time, and the measured clamp force versus time.

### Claim 6 (depends on 2)

The method of claim 2, wherein determining the mechanical characteristic function further comprises:
determining a general form of the mechanical characteristic function, wherein the general form of the mechanical characteristic function models nominal mechanical dynamics of the vehicle brake-by-wire unit, wherein the general form of the mechanical characteristic function is a third-order polynomial, and wherein the general form of the mechanical characteristic function is characterized by a plurality of mechanical system parameters; and
estimating a value for each of the plurality of mechanical system parameters based at least in part on the requested actuator displacement versus time and the measured clamp force versus time.

### Claim 7 (depends on 6)

The method of claim 6, wherein estimating the value for each of the plurality of mechanical system parameters further comprises:
estimating the value for each of the plurality of mechanical system parameters using a nonlinear least-squares regression based at least in part on the requested actuator displacement versus time and the measured clamp force versus time.

### Claim 8 (depends on 2)

The method of claim 2, wherein determining the performance of the vehicle brake-by-wire unit further comprises:
determining a first expected clamp force based at least in part on a requested clamp force value and the end-to-end characteristic transfer function;
determining a second expected clamp force based at least in part on an actuator displacement value and the mechanical characteristic function;
determining a first clamp force deviation between the first expected clamp force and a measured clamp force value;
determining a second clamp force deviation between the second expected clamp force and the measured clamp force value; and
determining the performance of the vehicle brake-by-wire unit based at least in part on the first clamp force deviation and the second clamp force deviation.

### Claim 9 (depends on 8)

The method of claim 8, wherein performing the diagnostic action further comprises:
incrementing an end-to-end diagnostic maturation counter in response to determining that a magnitude of the first clamp force deviation is greater than or equal to a first predetermined threshold;
incrementing a mechanical diagnostic maturation counter in response to determining that a magnitude of the second clamp force deviation is greater than or equal to a second predetermined threshold;
comparing the end-to-end diagnostic maturation counter to an end-to-end maturation threshold;
comparing the mechanical diagnostic maturation counter to a mechanical maturation threshold, wherein the mechanical maturation threshold is less than the end-to-end maturation threshold; and
providing a diagnostic trouble code (DTC) in response to determining that the end-to-end diagnostic maturation counter is greater than or equal to the end-to-end maturation threshold OR that the mechanical diagnostic maturation counter is greater than or equal to the mechanical maturation threshold.

### Claim 10 (depends on 9)

The method of claim 9, wherein performing the diagnostic action further comprises:
displaying a warning indicator to an occupant of the vehicle in response to determining that the end-to-end diagnostic maturation counter is greater than or equal to the end-to-end maturation threshold OR that the mechanical diagnostic maturation counter is greater than or equal to the mechanical maturation threshold.

### Claim 11

A vehicle brake-by-wire diagnostic system, the vehicle brake-by-wire diagnostic system comprising:
a vehicle brake-by-wire unit having a vehicle brake clamp force sensor;
a vehicle controller in electrical communication with the vehicle brake-by-wire unit, wherein the vehicle controller is programmed to:
determine a first expected clamp force based at least in part on a requested clamp force value and an end-to-end characteristic transfer function, wherein the end-to-end characteristic transfer function models nominal overall system dynamics of the vehicle brake-by-wire unit;
determine a second expected clamp force based at least in part on an actuator displacement value and a mechanical characteristic function, wherein the mechanical characteristic function models nominal mechanical dynamics of the vehicle brake-by-wire unit;
determine a first clamp force deviation between the first expected clamp force and a measured clamp force value measured by the vehicle brake clamp force sensor;
determine a second clamp force deviation between the second expected clamp force and the measured clamp force value measured by the vehicle brake clamp force sensor;
determine a performance of the vehicle brake-by-wire unit based at least in part on the first clamp force deviation and the second clamp force deviation; and
perform a diagnostic action based at least in part on the performance of the vehicle brake-by-wire unit, wherein the diagnostic action includes limiting a maximum speed of the vehicle in response to identifying a diagnostic trouble code (DTC).

### Claim 12 (depends on 11)

The vehicle brake-by-wire diagnostic system of claim 11, further comprising a reference brake-by-wire unit having a reference brake clamp force sensor and a reference brake actuator displacement sensor, and further comprising a reference controller in electrical communication with the reference brake-by-wire unit, wherein the reference controller is programmed to:
record a reference excitation profile of the reference brake-by-wire unit, wherein the reference brake-by-wire unit is a known healthy brake-by-wire unit, and wherein the reference excitation profile includes a requested clamp force versus time, a corresponding requested actuator displacement versus time, and a measured clamp force versus time;
determine the end-to-end characteristic transfer function based at least in part on the requested clamp force versus time and the measured clamp force versus time; and
determine the mechanical characteristic function based at least in part on the requested actuator displacement versus time and the measured clamp force versus time.

### Claim 13 (depends on 12)

The vehicle brake-by-wire diagnostic system of claim 12, wherein to determine the end-to-end characteristic transfer function, the reference controller is further programmed to:
determine a general form of the end-to-end characteristic transfer function to be a rational fractional polynomial:
H
end
-
end
=
b
0
⁢
s
m
+
b
1
⁢
s
m
-
1
+
⋯
+
b
m
s
n
+
a
1
⁢
s
n
-
1
+
⋯
⁢
a
n
·
e
-
T
d
⁢
s
wherein Hend-end is the end-to-end characteristic transfer function, s is a complex frequency variable, and the m, n, b, a, and Td factors are a plurality of end-to-end system parameters, and wherein the general form of the end-to-end characteristic transfer function models nominal overall system dynamics of the vehicle brake-by-wire unit; and
estimate a value for each of the plurality of end-to-end system parameters based at least in part on the requested clamp force versus time and the measured clamp force versus time.

### Claim 14 (depends on 13)

The vehicle brake-by-wire diagnostic system of claim 13, wherein to estimate the value for each of the plurality of end-to-end system parameters, the reference controller is further programmed to:
estimate a preliminary value for each of the plurality of end-to-end system parameters using a least-squares regression based at least in part on the requested clamp force versus time and the measured clamp force versus time; and
estimate the value for each of the plurality of end-to-end system parameters using a nonlinear optimization based at least in part on the preliminary value for each of the plurality of end-to-end system parameters, the requested clamp force versus time, and the measured clamp force versus time.

### Claim 15 (depends on 14)

The vehicle brake-by-wire diagnostic system of claim 14, wherein to determine the mechanical characteristic function, the reference controller is further programmed to:
determine a general form of the mechanical characteristic function, wherein the general form of the mechanical characteristic function models nominal mechanical dynamics of the vehicle brake-by-wire unit, wherein the general form of the mechanical characteristic function is a third-order polynomial, and wherein the general form of the mechanical characteristic function is characterized by a plurality of mechanical system parameters; and
estimate a value for each of the plurality of mechanical system parameters based at least in part on the requested actuator displacement versus time and the measured clamp force versus time.

### Claim 16 (depends on 15)

The vehicle brake-by-wire diagnostic system of claim 15, wherein to estimate the value for each of the plurality of mechanical system parameters, the reference controller is further programmed to:
estimate the value for each of the plurality of mechanical system parameters using a nonlinear least-squares regression based at least in part on the requested actuator displacement versus time and the measured clamp force versus time.

### Claim 17 (depends on 11)

The vehicle brake-by-wire diagnostic system of claim 11, wherein to perform the diagnostic action, the vehicle controller is further programmed to:
increment an end-to-end diagnostic maturation counter in response to determining that a magnitude of the first clamp force deviation is greater than or equal to a first predetermined threshold;
increment a mechanical diagnostic maturation counter in response to determining that a magnitude of the second clamp force deviation is greater than or equal to a second predetermined threshold;
compare the end-to-end diagnostic maturation counter to an end-to-end maturation threshold;
compare the mechanical diagnostic maturation counter to a mechanical maturation threshold, wherein the mechanical maturation threshold is less than the end-to-end maturation threshold; and
provide the diagnostic trouble code (DTC) in response to determining that the end-to-end diagnostic maturation counter is greater than or equal to the end-to-end maturation threshold OR that the mechanical diagnostic maturation counter is greater than or equal to the mechanical maturation threshold.

### Claim 18

A method for diagnostic monitoring of a vehicle brake-by-wire system, the method comprising:
recording a reference excitation profile of a reference brake-by-wire unit, wherein the reference brake-by-wire unit is a known healthy brake-by-wire unit, and wherein the reference excitation profile includes a requested clamp force versus time, a corresponding requested actuator displacement versus time, and a measured clamp force versus time;
determining an end-to-end characteristic transfer function based at least in part on the requested clamp force versus time and the measured clamp force versus time;
determining a mechanical characteristic function based at least in part on the requested actuator displacement versus time and the measured clamp force versus time;
determining a performance of a vehicle brake-by-wire unit based on the end-to-end characteristic transfer function and the mechanical characteristic function;
performing a diagnostic action based at least in part on the performance of the vehicle brake-by-wire unit, wherein the diagnostic action includes providing a diagnostic trouble code (DTC) based at least in part on the performance of the vehicle brake-by-wire unit; and
limiting a maximum speed of the vehicle based at least in part on the DTC.

### Claim 19 (depends on 18)

The method of claim 18, wherein determining the end-to-end characteristic transfer function and the mechanical characteristic function further comprises:
determining a general form of the end-to-end characteristic transfer function to be a rational fractional polynomial:
H
end
-
end
=
b
0
⁢
s
m
+
b
1
⁢
s
m
-
1
+
⋯
+
b
m
s
n
+
a
1
⁢
s
n
-
1
+
⋯
⁢
a
n
·
e
-
T
d
⁢
s
wherein Hend-end is the end-to-end characteristic transfer function, s is a complex frequency variable, and the m, n, b, a, and Td factors are a plurality of end-to-end system parameters;
estimating a value for each of the plurality of end-to-end system parameters based at least in part on the requested clamp force versus time and the measured clamp force versus time;
determining a general form of the mechanical characteristic function, wherein the general form of the mechanical characteristic function models nominal mechanical dynamics of the vehicle brake-by-wire unit, wherein the general form of the mechanical characteristic function is a third-order polynomial, and wherein the general form of the mechanical characteristic function is characterized by a plurality of mechanical system parameters; and
estimating a value for each of the plurality of mechanical system parameters based at least in part on the requested actuator displacement versus time and the measured clamp force versus time.

### Claim 20 (depends on 19)

The method of claim 19, wherein determining the performance of the vehicle brake-by-wire unit and performing the diagnostic action further comprises:
determining a first expected clamp force based at least in part on a requested clamp force value and the end-to-end characteristic transfer function;
determining a second expected clamp force based at least in part on an actuator displacement value and the mechanical characteristic function;
determining a first clamp force deviation between the first expected clamp force and a measured clamp force value;
determining a second clamp force deviation between the second expected clamp force and the measured clamp force value; and
determining the performance of the vehicle brake-by-wire unit based at least in part on the first clamp force deviation and the second clamp force deviation;
incrementing an end-to-end diagnostic maturation counter in response to determining that a magnitude of the first clamp force deviation is greater than or equal to a first predetermined threshold;
incrementing a mechanical diagnostic maturation counter in response to determining that a magnitude of the second clamp force deviation is greater than or equal to a second predetermined threshold;
comparing the end-to-end diagnostic maturation counter to an end-to-end maturation threshold;
comparing the mechanical diagnostic maturation counter to a mechanical maturation threshold, wherein the mechanical maturation threshold is less than the end-to-end maturation threshold; and
providing the diagnostic trouble code (DTC) in response to determining that the end-to-end diagnostic maturation counter is greater than or equal to the end-to-end maturation threshold OR that the mechanical diagnostic maturation counter is greater than or equal to the mechanical maturation threshold.