The primary task of the electronic pressure (E/P) valves is to control the pressure continuously in different industrial automation processes. Their use in pneumatic drives allows regulating pressures in both cylinder chambers and so it is possible to achieve a direct force controlled actuator. Additionally to the force control, position control of the pneumatic actuator using E/P valves has been presented. A dynamic model for control purposes of the process has been derived, followed by the PID controller tuned according to damping optimum criteria. The control algorithms have been experimentally verified on an industrial cylindrical rod-less actuator controlled by two E/P valves. The control performances are comparable with the set-up with proportional directional control valves (servo-valves). Based on the experimental results, it can be concluded that these valves have potential for successful implementation in industry for position and force control applications.

The fuzzy logic controller, which uses an analytic activation function for the defuzzification procedure, was applied to the position control of a servo pneumatic drive controlled by a proportional valve. The Gaussian shape of input fuzzy sets, with the possibility of their modification, was used to fuzzify the input signal. The control signal was determined by introducing an analytic function instead of defining the fuzzy rule base. In this way, a conventional 2-D fuzzy rule table base is modified into 1-D fuzzy defuzzification based on an analytic function to calculate the controller output. In this control algorithm, the problem of conventional fuzzy logic control, in terms of the exponential growth in rules as the number of input variables increases, is eliminated. The synthesis controller procedure is adjusted to the flow rate characteristic of the proportional valve. The developed control algorithms are verified by computer simulation and by testing on a real pneumatic rodless cylindrical drive.

The paper presents the results of modeling and control of an original and unique ball-on-beam system with a pneumatic artificial muscle pair in an antagonistic configuration. This system represents a class of under-actuated, high-order nonlinear systems, which are characterized by an open-loop unstable equilibrium point. Since pneumatic muscles have elastic, nonlinear characteristics, they are more difficult to control. Considering that an additional nonlinearity is added to the system which makes it harder to stabilize. The nonlinear mathematical model has been derived based on the physical model of the ball-on-beam mechanism, the beam rotating by using an antagonistic muscle pair and the pneumatic muscle actuated by a proportional valve. Based on the nonlinear model, the linearized equations of motion have been derived and a control-oriented model has been developed, which is used in the state feedback controller design procedure. The proposed state feedback controller has been verified by means of computer simulations and experimentally on the laboratory setup. The simulation and experimental results have shown that the state feedback controller can stabilize the ball-on-beam system around an equilibrium position in the presence of external disturbances and to track a reference trajectory with a small tracking error.

The paper presents a hypothetical conversion of a conventional cable skidder powertrain to its hybrid version. Simulations of skidder operation were made for two existing forest paths, based on the technical characteristics of the engine, transmission system and the characteristics of the winch. Fuel and time consumption were calculated per working cycle considering the operating conditions (slope, load mass). The model was then converted to a hybrid version by adding a battery energy storage system in parallel with the electrical power generator and by employing an energy management control strategy. The dimensions of the battery and the power generator were chosen based on the characteristics of the existing winch with the aim of completely taking over its operation. The management strategy was selected using the specific fuel consumption map. All simulations were repeated for the hybrid drive under the same operating conditions. The results show that fuel savings of around 13% can be achieved with the selected hybrid drive and steering strategy.

Over the last decade, off-road vehicles have been increasingly hybridized through powertrain electrification in terms of additional electrical machine-based propulsion and battery energy storage, with the goal of achieving significant gains in fuel economy and reductions in greenhouse gases emissions. Since hybrid powertrains consist of two or more different energy sources and may be arranged in many different configurations, there are many open questions in their design and powertrain energy management control, which may have influence on the hybridized powertrain purchase cost and efficiency. This paper presents simple backward optimization models of conventional and hybrid cable skidder powertrains. These models are then used in the optimization of control variables over one forest path in order to find the minimum possible fuel consumption. The optimization results show that 15% fuel efficiency improvement in winching and skid trail driving can be achieved with the selected hybrid powertrain. With that improvement, main hybrid drive components can be paid off in 13 years.

This paper investigates potential uses of a novel direct driven electro-hydraulic systems for articulated forestry tractors (skidders), due to these systems having notably higher energy efficiencies compared to classical electro-hydraulic systems that are currently being used in skidders for steering, lifting the front and the rear plate, as well as for operating the double-drum winch. A detailed analysis of the skidder rear plate mechanism is carried out, and static force profiles of hydraulic cylinders are obtained for the rear plate based on mechanism dynamics and measurement data from the literature. Thus, obtained results have been used to emulate the real-life force profiles in laboratory experiments featuring both the classical and the proposed direct driven hydraulic systems for the purpose of comparative analysis of their energy and fuel efficiency. These results are subsequently used to estimate the skidder fuel consumption and possible fuel savings over the entire vehicle life span for the realistic vehicle utilisation scenario. The main result is that fuel consumption can be reduced up to five times in the case of direct driven hydraulic system, thus effectively resulting in return of investment period of about four years in the case of skidder being retrofitted with direct driven hydraulic system.