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A hierarchical lane-keeping controller of passenger cars is analyzed, with the consideration of feedback delay in the control loop. The higher-level controller generates the desired steering angle based on the delayed feedback of the lateral position and yaw angle of the vehicle. The feedback delay of the lateral position and the yaw angle are treated separately in the model, therefore more general sensor setups and estimation algorithms can be handled. A lower-level proportional-integral-derivative power steering controller ensures that the desired steering angle signal is followed properly. The linear stability analysis of the resulting closed-loop system is performed, with a focus on the controller parameters and the delay values. The optimal control gains, leading to the fastest decay of the solution are also investigated in detail. The results are showcased with the help of stability charts and numerical simulations.

The dynamical properties of the main spindle of a milling machine can have essential effect on the stability of milling processes. These dynamical properties often change with the rotational speed of the spindle, e.g. the stiffness and damping properties of the angular contact bearings of the spindle vary significantly with the spindle speed. Our study focuses on the development of measurement devices which enable us to measure the dynamical properties of rotating spindles with high accuracy. The concept of the Fotonic Beam Reduction (FBR) laser sensor is presented, which is applied to measure the displacement of rotating milling tools in a contactless way. In order to determine the frequency response function (FRF) of the spindle, a ball shooter is constructed. The impulse generated by the bullet on the target is analysed experimentally. A force sensor is utilized to estimate the time interval of the impacting between bullet and surface. It is shown that the repeatability of the impact is very good, and the generated impulse can excite the natural frequencies up to 30 kHz. The FBR sensor with the ball shooter is applied to identify the FRF of a milling spindle versus its rotational speed. The variation of the vibration frequencies is demonstrated by means of the experiments.

A hardware-in-the-loop (HIL) experimental setup is presented to analyze the stability of turning process. In our test rig, the dummy workpiece in the spindle can be excited in radial direction by an electromagnetic contactless actuator. This actuator is utilized to emulate the contact (cutting) force that acts originally between the tool and workpiece in case of a real process. In the HIL test, the displacement of the dummy workpiece is measured with the help of an optical sensor. A high performance real target computer is used to calculate the theoretical cutting force based on the present and past values of the relative displacements of the dummy workpiece. For the sake of simplicity, linear cutting force characteristics is implemented together with the emulated surface regeneration effect. In the HIL test, the loss of linear stability is detected for various real spindle speeds and virtual depth of cut, namely, the theoretically predicted pattern of the instability lobes is verified.

The lateral vibration of towed wheels—so-called shimmy—is one of the most exciting phenomena of vehicle dynamics. We give a brief description of a simple rig of elastic tire that was constructed for laboratory measurements. A full report is given on the experimental investigation of this rig from the identification of system parameters to the validation of stability boundaries and vibration frequencies of shimmy motion. The experimental results confirm the validity of those tire models that include delay effects. A peculiar quasiperiodic oscillation detected during the experiments is explained by numerical simulations of the nonlinear time-delayed mathematical model.