This paper presents the results of experimental research on rolling resistance forces occurring during the motion of omnidirectional wheels equipped with dual rows of passive rollers. Due to the complexity of wheel–surface interactions and the stochastic nature of contact transitions, such wheels are often characterized experimentally rather than analytically. A custom-built test stand was used to measure resistance forces for different wheel orientations (0°, 30°, 45°, 60°, and 90°) and two vertical loads (117.7 N and 215.8 N) on two surface types: industrial concrete and anodized aluminum. The results demonstrated a strong influence of wheel orientation on resistance, with the highest mean force recorded at 60° for both loads. The results revealed an oscillatory pattern in the resistance force, strongly influenced by the angular position of the wheel. For concrete, mean forces ranged from 1.04 N to 10.34 N, while for aluminum, they ranged from 1.08 N to 10.11 N. Significant oscillations and occasional negative force values were observed, attributed to roller geometry and wheel irregularities. The data obtained are useful for validating numerical models and improving the design and control of mobile robots using omnidirectional wheels.

Different types of devices, from the simplest (medical walkers) to the most technologically advanced ones (mechatronic devices), are widely used to support the rehabilitation process for people who suffered strokes or have other disabilities—especially to enhance their mobility. This article presents a new mechatronic system for gait reeducation, which consists of two main components: training treadmill and body weight support system. The device is also equipped with sensors for measuring the rope inclination angle, rope tension and foot pressure on the ground. The transmission of measurement and control signals between the computer with control system and the electromechanical part of the device is realized by means of three real-time boards. This publication covers certain issues related to the device design process, integration of the main components, as well as the description of the developed treadmill speed adaptation algorithm and experimental verification of such control system. The speed of treadmill belt is adjusted by a feedback loop with a rope inclination angle measurement. Because of the kind of the connection of the treadmill (the control signals are sent to the buttons in the treadmill control panel) and related limitations, a proper conversion of the control signal was required, from a continuous one to a digital square wave signal with variable period. Developing an optimal treadmill speed control algorithm in this case was an interesting engineering challenge.

Computational optimization and implementation of control system for mechatronic treadmill with body weight support system

This article concerns the stability analysis of a control system for a dynamic body weight support system in a rehabilitation device for the re-education of human gait. The paper presents a physical model of the device, which characterizes the most important physical phenomena associated with the movement of the system, i.e., inertia, damping, and elasticity. The device has one active and one passive element. They are connected by a connector with elastic and damping properties. This solution provides the kinematic chain required due to interactions with humans, while at the same time ensures that the device is an underactuated system. The article also presents the methodology used to verify the stability of the control system while acting as an active body weight support system. The paper formulates the mathematical model of the system that was used in the synthesis of control using the Lyapunov theory of stability. The results of simulation and experimental tests are also presented.

The article presents a comparison of the methods of modeling the underactuated ball and beam system. This study was carried out to select a model suitable for the development of a control system using the model-based design methodology. Firstly, the approach commonly used in research was verified. It was also examined whether it is important to take into account the eccentric fixation in these models. An original model taking into account friction resistance was also proposed. The considered models were simulated in Matlab/Simulink software environments and verified in reality. The obtained results were compared and analyzed.

This paper discusses the stability of systems controlling patient body weight support systems which are used in gait re-education. These devices belong to the class of underactuated mechanical systems. This is due to the application of elastic shock-absorbing connections between the active part of the system and the passive part which impacts the patient. The model takes into account properties of the system, such as inertia, attenuation and susceptibility to the elements. Stability is an essential property of the system due to human–device interaction. In order to demonstrate stability, Lyapunov’s theory of stability, which is based on the model of system dynamics, was applied. The stability of the control system based on a model that requires knowledge of the structure and parameters of the equations of motion was demonstrated. Due to inaccuracies in the modeling of the rope (one of the basic elements of the device), an adaptive control system was introduced and its stability was also proved. The authors conducted simulation and experimental tests that illustrate the functionality of the analyzed control systems.