CS201293B1 - Device for contactless exciting of mechanical systems and simmultaneous measuring of the exciting force - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a device for contactless excitation of mechanical systems and simultaneously measuring excitation force.

Dynamic parameters of mechanical systems can be determined from the results of experimental measurements if their complex responses are known depending on the amplitude and frequency of excitation. At present, electrodynamic, capacitive or electromechanical vibrators with force sensors are used for defined excitation of mechanical systems, mostly based on piezoelectric principle. In these cases, the force transducers must be mechanically fixed between the excited system and the vibrator, which in many cases is a source of measurement errors and other implementation difficulties. A certain amount of additional weight between the force sensor and the measured system makes the force indicated by the force sensor not exact. Part of the measured force is consumed to “accelerate” this unwanted extra weight. Excitation of the object in the desired location and direction is very problematic. If the excitation force is applied in the desired direction, then all remaining orthogonal types of movement must be allowed at the excited point of the system without restriction. Such limited realization by mechanical connection of the force transducer and the vibrator constitutes inadvertent and undesirable coupling excitation. The mechanical connection of the force transducer to the excited system can be very time consuming. In most cases, the connection cannot be made in such a way that the system is not impaired for its original functional use. Virtually insurmountable mechanical coupling problems arise in very few material systems that are desirable to drive to very high frequencies. The applicability of high-end electrodynamic vibrators is frequency limited by the upper limit of 20 kHz. However, this frequency limit is very low for many engineering products and unsatisfactory due to practical needs.

The above-mentioned disadvantages are eliminated by a device for contactless excitation of mechanical systems and simultaneous measurement of excitation force formed by a contactless vibrator according to the invention, which is characterized in that the contactless vibrator mounted on a flexible suspension is firmly connected to an accelerometer oriented in the direction of excitation.

An exemplary embodiment is schematically illustrated in the accompanying drawing, wherein Fig. 1 represents an arrangement using an electromagnetic or capacitive non-contact vibrator and Fig. 2 represents an arrangement using an electrodynamic non-contact vibrator.

The contactless vibrator 1 is electromagnetic, capacitive or electrodynamic is located at a corresponding distance from the object to be measured 3 on the flexible suspension 2 and is firmly connected to the accelerometer 5 oriented in the direction of excitation. The flexible hinge 2 is formed, for example, by a membrane, a foil or a set of magnets. In the case of using an electrodynamic vibrator (Fig. 2), the coils 4 of the non-contact vibrator 1 are bonded to the measured object 3.

In operation, the elastic suspension 2 of a certain stiffness C allows the contactless vibrator 1 of mass M to oscillate in the direction of excitation x. If the coil of the vibrator 1 is supplied with an alternating current of frequency ω, an alternating excitation force F of frequency ω is generated between the contactless vibrator 1 and the measured object 3. At the same time, the accelerometer 5, fixed to the non-contact vibrator 1, indicates the acceleration x. If we know the acceleration value x, the mass M of the vibrator 1 placed on the hinge 2 with the stiffness C, then we determine the excitation force from the relation F = Mx (1--), where M is the mass of the vibrator with accelerometer, x is the acceleration direction of excitation, ωι is the natural circular frequency and ω is the circular frequency of the excitation, with the natural frequency ωχ

where C is the stiffness of the suspension 2 and M the weight of the vibrator 1 with the accelerometer 5. In cases where the intrinsic circular frequency ωχ is considerably lower than the circular excitation frequency ω, the excitation force is determined from F = Mx where M is the vibrator mass 1 s The accelerometer 5 ax is the acceleration of the oscillating motion in the direction of excitation.

The invention can be used in demanding laboratory measurements, in routine measurements in development and manufacturing, especially wherever high frequency excitation is required.

Claims (1)

Device for contactless excitation of mechanical systems and simultaneous measurement of excitation force formed by a contactless vibrator, characterized in that the contactless vibrator (1) mounted on a flexible suspension (2) is firmly connected to the accelerometer (5) oriented in the direction of excitation.