## 1 Introduction
The paper presents experimental and simulation results, but only for two types of faults: gain and offset fault. These are failures that do not significantly affect the entire control structure. Paper [22] describes the use of a different type of observer--the extended Kalman filter (EKF). Detection is performed by comparing the estimated values with the measured ones. The work presents experimental results for one type of current sensor fault--a signal loss for one speed value. The detection of current and speed sensors is described in the article [23]. Two types of observers are used for this purpose: high-order sliding mode (HOSM) and Luenberger observer (LO). LO is responsible for current estimation. The measurement of speed and \(\alpha\), \(\beta\) voltages were used for estimation. These values are compared with the measured values of stator currents; if the difference between them exceeds a certain fixed value, it means a failure in the corresponding phase. In the work under experimental conditions, the detection of signal loss in phase A was shown. Signal-based methods do not require knowledge of the object model [24]. Once implemented, the algorithm is a universal solution for motors with different parameters. These algorithms are also usually of low computational complexity and can be easily implemented in a signal processor. These are their most important advantages. An example of a signal-based method can be seen in the research presented in [25]. The detection and localization of the current sensors are based on current measurements. The authors described a simple detector that compares average normalized values of the phase currents in three phases. The phase shift between the remaining phases after the failure occurred is also taken into account. Only the detection of the measurement signal loss is considered in the research. This method is also described in [26]. Another simple solution is shown in the article [27]. The authors used the fact that in the event of a failure of one of the current sensors, the phase shift between the other two changes and the sign of current value (SCV) is also used for detection. A method based on signal measurements is also described in the article [28]. Current sensor fault detection is based on the measurement of the voltage in the intermediate circuit. There are also examples in the literature where detection is based on the measurement of other quantities, such as current [25] or rotor position. There are also works in which the measurement of several signals is used to detect faults in current sensors [29]. This article describes a method based on measurement signals. It uses only the current measurement to detect faults in the current sensors. The method consists of determining the so-called current markers and then comparing their values. The method was previously described for induction motors [24]. Simulation tests for the PMSM in field-oriented control and experimental results in scalar control are also presented [30]. The fault diagnostic system was tested in simulation in two control algorithms--the scalar control and vector control--to demonstrate the transient of faulted signals, detection signals, and detection time. In this position, it is shown that after current sensor fault appearance, its influence on the control structure, especially speed transient, is compensated using non-sensitive components. The analysis is presented for all the above-mentioned faults for different speed conditions. This study describes its application in experimental research in the control structure field-oriented control (FOC). In FOC, when one of the sensors fails, it affects the entire control structure. After fault high currents appear, the rated values are exceeded several times. This definitely makes it difficult to locate the failure. Each sensor shows an abnormal value. That is why it is so important to conduct experimental research in a closed-loop structure.