Natural aging of commercial triaxial low-g MEMS accelerometers, manufactured by surface micromachining, was evaluated in terms of changes of their offset voltages and scale factors, assigned to each sensitive axis. Two pieces of two models of triaxial accelerometers (ADXL 330 and ADXL 327 by Analog Devices Inc.) with analog outputs were tested within a period of ca. 4.5 years. Two different computer-controlled test rigs were used for performing relevant experimental studies, employing tilt angles as the reference source. Methodology of determining the proposed indicators of aging was based on cyclic repetition of the calibration procedure for each accelerometer. Changes of the output signals of the tested accelerometers were observed, resulting in respective indication errors of ca. 0.8% or even 2.2% while related to determining tilt. Since the accelerometers were operated under mild conditions while tested, much bigger errors are to be expected in the case of harsh conditions. Both pieces of ADXL 330 accelerometers ceased to operate properly within the testing period, approximately at the same time, for no apparent reason; thus, it is recommended to introduce redundancy in relevant reliable measuring circuits by doubling the number of the applied accelerometers.

Mechatronics is nowadays a dominating concept in design of various kinds of systems and technical devices. High speeds of data processing by control units of mechatronic systems, as well as high dynamics of their actuators allow the systems to be applied in wider fields. This refers to the medicine as well, especially while making attempts to replace lost human motor abilities by means of robots aiding the man. These devices can be divided into three groups: exoskeletons designed to strengthen the natural force of human muscles, orthotic robots that restore lost or weakened functions of human limbs, and prosthetic robots replacing an amputated limb. The first and the third group are known quite well, whereas the orthotic robots are at an initial phase of their development. The authors have worked on a device for aiding the motion of disabled people suffering from paresis of the lower limbs. The paper presents a concept and a structure of the system that has been created, comparing it with similar devices that have already existed. There are indicated some connections and areas where the subunits merge, as well as the rules of their working with the user.

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Values of static and kinetic friction coefficient in micro slide bearings, consisting of journals and bushings (with the diameter of 3.5 mm) made of pairs of 5 polymer materials (16 chosen combinations of PA11, ABS, PC, PS and PETP), were determined. A method of measuring static and kinetic friction coefficient, at various values of: load, rotational speed, and standstill time, as well as the structure of a dedicated test rig, were discussed. Chosen mechanical properties of polymers measured using indentation method, and conclusions from the conducted experiments, are shown. The presented results provide key information for a proper choice of polymer materials, which are to work as a friction node. The biggest observed difference in the moment of friction among the tested slide bearings reached almost 40% (with respect to the highest value).

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