Introduction. Pantograph mechanisms are the most widely used parallel kinematic mechanisms. Their advantages include a single-drive architecture, high dynamic performance, and high positioning accuracy. The application of pantograph mechanisms is increasingly expanding in mobile robotic platforms and scissor lifts. Nevertheless, these mechanisms exhibit complex dynamic behavior and require sophisticated analytical and numerical approaches. Consequently, their analysis and modeling, especially considering energy-efficiency requirements, constitute an important practical research problem.
Methods. General methods of static and kinematic analysis were employed in this study. A calculation scheme was formulated, and analytical expressions were derived along with graphical representations of the support reactions, actuator force (driving force), and additional elastic forces as functions of the lever rotation angle.
Results. The scissor lift design additionally incorporates upper and lower extension and compression springs to unload the actuator implemented as a sliding screw–nut transmission. The stiffness coefficients of the additional springs were determined, and their operating conditions were taken into account. In the lower position of the pantograph mechanism, the upper spring is maximally extended; therefore, its force reaches a maximum value. During lifting, this force gradually decreases and becomes zero in the upper position of the platform. The lower spring is maximally compressed in the lower position of the platform and extends during platform lifting and lever rotation up to an angle of α = 25°. Consequently, the influence of the lower spring on the levers is limited, whereas its elastic force magnitude exceeds that of the upper spring. The incorporation of these springs results in a 55.2% reduction in actuator force and a 59.4% reduction in internal forces compared to the configuration without springs.
Conclusions. The incorporation of additional springs into the pantograph lifting mechanism design is justified as an effective approach to reducing the actuator force and the reactions in the supports and joints.
