Infinitely Variable Transmission Research Articles

Systematic modeling of complex time-variant gear systems using a Power-Oriented approach

This paper addresses a methodology for the systematic modeling of complex gear systems. The methodology is based on the use of a unified general model, working for all complex gear systems: time-variant as well as time-invariant, having parallel or oblique rotation axes. The model equations are automatically written following the outlined procedure and applying the presented algorithms, making this approach less prone to mistakes with respect to other approaches. Next, a reduced model assuming rigid gear connections and introducing no loss of information is proposed, which directly gives the kinematic relations between the gears angular speeds and input torques. In order to show some case studies, the proposed methodology is applied to three systems of interest for vehicle dynamics and powertrain modeling. The considered case studies are a differential structure having a bevel gearing system with non-perpendicular gear shafts, a vehicle differential and a full toroidal variator, which is suitable for applications such as KERS (Kinetic Energy Recovery System) and IVT (Infinitely Variable Transmission). Furthermore, the control of a full toroidal variator acting as a KERS with reference to an automotive case study and the comparison of the proposed modeling methodology with two other approaches are addressed.

Reliability-Informed Economic and Energy Evaluation for Bi-Level Design for Remanufacturing: A Case Study of Transmission and Hydraulic Manifold

AbstractDesign for remanufacturing (DfRem) is one attractive strategy that encourages the reuse of a product and extends the product's life cycle. Traditional design processes often only consider product reliability at an early design stage. However, from the perspective of environmental sustainability, it is becoming increasingly important to evaluate the long-term economic and environmental impacts of design decisions during early-stage design. We propose a bi-level DfRem framework consisting of system-level reusability allocation and component-level design tradeoff analysis, considering reliability and product warranty policy. First, a system-level reusability allocation problem aims at a theoretical exploration of the design space where all the components comprising the system are allocated certain reuse rates to achieve target energy savings with minimum cost. Following the theoretical exploration at the system level, a component-level analysis looks at practical design options for each component and trades-off between the overall cost and energy consumption for multiple remanufacturing cycles. Both levels of the framework require modeling component reuse for multiple remanufacturing cycles, which we achieve by using a branched power-law model that provides probabilistic scenarios of reusing the component or replacing it with a new part. We demonstrate the utility of this framework with the case study of an infinitely variable transmission (IVT) used by some agricultural machines manufactured by John Deere and show snapshots of a prototype software tool that we developed for easy use by designers.

Cam based Infinitely Variable Transmission Theoretic Modelling

Infinitely variable transmission (IVT) is a system which delivers the ratio between two turning elements to a continuous (non-discrete) variation (including zero). This article uses Solidworks software to build and simulate a cam-based IVT system. There are two identical units in the system under examination. Each unit comprises a cam with an oscillating slot connection that swings on a hinge and can be vertically shifted by changing the transmission rate. This modifier can be a power screw or a hydraulic ram. In addition, a grooved wheel and followers or an actuator are included in the system units. The raised wheels swing rotating movement, such that they are coupled by a single-way clutch to the output shaft (ratchet) to move the output shaft one way.During the performance research, cam shapes are considered and examined inside the mechanism. a mixture of the unchanging speed and 1-5 polynomial shapes, used for the current investigation and tailored forThe results produced from the simulation generally reveal the theoretical results expected in accordance with the layout of the current IVT system. For all parts in these units, the findings imply a uniform velocity while each unit is powered. In this investigation, nevertheless, the ratchets used cause remarkable fluctuations in the angular speed of the output axis. Further research is therefore urgently needed in the choice and investigation of more efficient ratchets.

Theoretical and experimental investigation on an integral time-delay feedback control combined with a closed-loop control for an infinitely variable transmission system

A nonlinear closed-loop speed ratio control combined with an integral time-delay feedback control is developed to adjust the speed ratio of an infinitely variable transmission (IVT) for a desired output speed with any variable input speed. The speed ratio control of the IVT system is developed based on its nonlinear dynamic model, which involves a forward speed controller and a crank length controller for varying operating conditions. The closed-loop forward speed controller can operate with efficient driving performance based on an optimal operation line of a prime mover. System identification is carried out to achieve high control performance of the IVT system. Comprehensive results of experimental investigation are presented to validate the proposed control strategy for the IVT system. An instrumented rotation speed measurement system is designed so that quantities necessary for the time-delay control variable can be measured. Experimental results show that the speed ratio of the IVT with the proposed control strategy can achieve an excellent tracking response for the desired constant output speed. This study reveals that fluctuations of the output speed of the IVT system can be reduced by time-delay feedback control.

Experimental Investigation on Control of an Infinitely Variable Transmission System for Tidal Current Energy Converters

High operation performance of a tidal current energy converter (TCEC) requires a gear transmission with a continuously variable speed ratio for low-speed and high-torque conditions. A nonlinear closed-loop control combined with an integral time-delay feedback control is developed to adjust the speed ratio of an infinitely variable transmission (IVT) system for TCECs. A speed ratio control for the IVT system involves a forward speed controller and a crank length controller for different tidal current speed ranges. The time-delay control is designed to reduce speed fluctuations of the output speed of the IVT with an accurate speed ratio. Experimental investigation was carried out to test the validity of the proposed control strategy for the IVT system. An instrumented rotation speed measurement system is designed so that quantities needed for the time-delay control variable can be measured. Experimental results show that the speed ratio of the IVT with the proposed control strategy can achieve an excellent tracking response for the desired constant output speed and reduce speed fluctuations of the output speed of the IVT by the time-delay feedback control.

Simulation of cam-based infinitely variable transmission

Infinitely variable transmission (IVT) is a system that gives a continuous (non-discrete) variation that includes zero in transmission ratios between two rotating elements. In this paper, a cam based IVT mechanism was designed and simulated using SolidWorks software containing two identical units. Each unit included a cam with a follower and oscillatory slotted links pivoted at a hinge that could be moved vertically by altering the transmission ratio, achieved by using a hydraulic ram or a power screw. system units also include a grooved wheel and a follower or actuator. During operation, the grooved wheels displayed an oscillating rotational motion, so that they are connected to the output shaft via one-way clutches (ratchets) to give the output shafts one-way directional motion. The cam profiles are designed and investigated within the system with regards to performance. A combination of uniform velocity and 1-5 polynomial profiles where selected and designed for the current study In general, the results obtained from the simulation showed compatibility with the expected theoretical results derived from the design of the current IVT system. These results indicated uniform velocity during the power stroke in each unit for all parts in the units. However, the ratchets used in this study produced a noticeable fluctuation in the angular velocity of the output shaft, and further work on the selection and development of more efficient ratchets is thus strongly recommended.

Design and power loss evaluation of a noncircular gear pair for an infinitely variable transmission

A novel noncircular gear design method is proposed in this work based on a modified high-order elliptical pitch curve for an infinitely variable transmission (IVT), and power loss evaluation of a noncircular gear pair is investigated. Modified high-order elliptical pitch curves of noncircular gears are developed by using kinematic equations of the IVT to eliminate cusps between every two neighboring lobes of pitch curves, and improve smoothness of pitch curves and manufacturability of the noncircular gear pair. A power loss evaluation method is developed for the noncircular gear pair by calculating sliding friction power loss of meshing tooth surfaces. The time-varying friction force of every contact position on meshing tooth surfaces of the noncircular gear pair is calculated by using their variable coefficients of friction and sliding velocities. The instantaneous sliding friction power loss of the noncircular gear pair is calculated based on time-varying friction forces and sliding velocities along contact paths of tooth profiles of the noncircular gear pair.

The Performance of One-Way Clutch in a Cam-Based Infinitely Variable Transmission

Continuously variable transmission is the system which provides a step-less change in transmission ratio between two rotating shafts. When it can provide zero ratio, it is known as infinitely variable transmission (IVT). These systems are mainly classified into two categories; traction and non-traction types. In the traction type, the power is transmitted by friction force that develops between the active elements in the mechanism, while in the non-traction systems, the power is transmitted via direct contact. A very common type of non-traction IVT is the cam-based system. In this type, the rotating motion of the input element is converted to oscillatory motion with continuously variable amplitude. Eventually, the oscillatory motion is rectified to one-way rotational motion by means of a one-way clutch (rectifier). The rectifier is considered an essential element in the IVT system, as it is subjected to an extreme dynamical condition. In this study, the performance of one-way clutches (rectifiers) in a cam-based IVT is presented. The IVT system under consideration is a combination of two identical units and in each one, a rectifier is fitted at the output shaft. It is required that this rectifier is able to efficiently transmit the power during its engagement. It should also generate minimal power loss during disengagements, when aggressive relative motion is presented between its parts. It has been found that the operation of the one-way clutch is mainly determined by the designed cam profile. For this study, the profile is a combination of constant speed and trapezoidal forms. It was also concluded that the value of the selected transmission ratio controls the amount of fluctuation in the acceleration, velocity and displacement and hence, the energy lost due to slippage of the clutches.

Modeling and theoretical analysis of a novel ratcheting-type cam-based infinitely variable transmission system

An infinitely variable transmission (IVT) is a system that allows for a continuous (non-discrete) variation (including zero) in transmission ratio between two rotating elements. In this paper, a novel ratcheting-type IVT mechanism is presented and its geometrical design and kinematic analysis are studied in details. The proposed system contains two identical units. Each unit includes a cam with a follower, oscillatory slotted links pivoted at a shaft that can be moved vertically by a hydraulic ram (alterable transmission ratio), and a grooved wheel with an actuating rod. The input rotational motion is converted through each unit to an oscillatory angular motion of controlled amplitude. This resulting motion is rectified using a ratchet to get a unidirectional output rotational motion. Therefore, the system output motion will have a different velocity and acceleration than those of the system input. The kinematic analysis revealed that the transmission ratio can be varied continuously in a range from zero to infinity. The analysis also showed that, for particular transmission ratios, the system gives uniform output (angular velocity and acceleration) for a corresponding uniform input.

Infinitely variable transmission with orbital pulleys

The purpose of this article is to propose an infinite variable transmission with orbital pulleys, which consists of two parallel transmission systems. The system comprises a planetary gear set and a continuously variable transmission. The principle of operation of the infinite variable transmission proposed in this article is based on the actuation of one half-sided pulley, which has a translational movement in a direction, and the same amount of movement is reproduced by the other half-sided orbital pulley in reverse to secure that the length of the belt remains constant. The fixed constant horizon enables the infinite variable transmission to change the transmission ratio from negative values to positive passing through zero in a continuous manner without using a clutch or interrupting the system. The dynamic model and prototype of the infinite variable transmission with orbital pulleys are developed for designing, controlling, and validating purposes. The model is obtained using the Euler–Lagrange methodology, and it is experimentally validated by comparing the proposed model with the experimental measures. The infinite variable transmission with orbital pulleys is controlled under different conditions; the experimental results show that the proposed design of infinite variable transmission provides robustness to maintain constant speeds at the output to changes at the input velocity.

Design and Analysis of a Novel Power-Split Infinitely Variable Power Transmission System

In the last few decades, power-split infinitely variable transmission (IVT) systems have attracted considerable attention as they ensure high driving comfort with high total efficiencies, especially in off-highway vehicles and agricultural machines. In this study, a novel power-split-input-coupled IVT system is developed. The effects of various dynamic parameters such as power flow and Willis transmission ratio on the mechanical efficiency of the systems are investigated. Kinematic analysis of the new system has been carried out. In addition power flow equations are derived as functions of the power that flows through the infinitely variable unit (IVU). The results indicate that the main parameters, which are strictly related to mechanical efficiency are the power and torque flows through the IVU.

Design-Parameters Setup for Power-Split Dual-Regime IVT

To analyze the working possibilities of power-split infinitely variable transmissions (IVTs) it is necessary to follow a systematic approach. The method proposed in this paper consists of generating a block diagram of the transmission and then, based on this diagram, to derive the kinematics and dynamics equations of the transmission. For an actual numerical case, the derived equations are used to find characteristic values of the transmission components (gear and chain drives, planetary units) necessary to calculate the speed ratios, the speeds, torques and powers acting on the shafts and coupling (control) elements, and even to estimate the overall efficiency of the transmission.

Design and Stability Analysis of an Integral Time-Delay Feedback Control Combined With an Open-Loop Control for an Infinitely Variable Transmission System

The kinematic model of an infinitely variable transmission (IVT) is introduced, and the nonlinear differential equation for the dynamic model of the IVT system with a permanent magnetic direct current (DC) motor and a magnetic brake is derived. To make the average of the input speed converge to a desired constant for any input power and output load, an integral time-delay feedback control combined with an open-loop control is used to adjust the speed ratio of the IVT. The speed ratio for the open-loop control is obtained by a modified incremental harmonic balance (IHB) method. Existence and convergence of a periodic solution are proved under a condition for parameters of the IVT system, and uniqueness of the periodic solution is proved by converting the nonlinear differential equation to a new differential equation that is Lipchitz in the dependent variable and piecewise continuous in the independent variable. A time-delay variable that is an approximation of the average of the input speed is used as the feedback to control the changing rate of the speed ratio. The IVT system with the time-delay control variable can be converted to a distributed-parameter system. Thus, the spectral Tau method is used to design the time-delay feedback control so that the IVT system is locally exponentially stable. The static error from the open-loop control is eliminated; the feedback control variable with time-delay is smoother than that without time-delay, which yields a lower control effort and more robust control design, since the time-delay variable that acts as a low-pass filter reduces the effect of the instantaneous change of the IVT system.

Application of Multi-speed Gearbox in Infinitely Variable Transmission

One way to reduce vehicles’ fuel consumption (FC) is to optimize different parts of its powertrain. Among different modern powertrains, continuously variable transmission (CVT) is one of the common types which changes speed ratio between engine and wheels, continuously. Therefore, the CVT allows the engine to operate at its fuel-optimal speed. Due to the limited power transmission capacity and speed ratio range of the CVT, researchers attempted to combine the CVT with a planetary gear train and a fixed ratio mechanism. This mechanism is called infinitely variable transmission (IVT). In this study, a multi-speed gearbox (MSG) is used in the IVT and its impact on the powertrain performance and the vehicle’s FC is investigated. After extracting the governing dynamics of the system, an optimization on the parameters which affect the IVT performance is implemented to minimize the vehicle’s FC. It is observed that the vehicle’s FC for the case of using the optimized IVT equipped with two-speed MSG is almost 5% less than the case of using the optimized six-speed AT transmission in different driving cycles.

Dynamic Analysis of a Geared Infinitely Variable Transmission

Dynamic analysis of a geared infinitely variable transmission (IVT) that can generate a continuous output-to-input speed ratio from zero to a certain value is studied for vehicle and wind turbine applications. With the IVT considered as a multirigid-body system, the Lagrangian approach is used to analyze its speeds and accelerations, and the Newtonian approach is used to conduct force analysis of each part of the IVT. Instantaneous input and output speeds and accelerations of the IVT have variations in one rotation of its input shaft. This work shows that the instantaneous input speed has less variation than the instantaneous output speed when the inertia on the input side is larger than that on the output side and vice versa. The maximum torque on the output shaft that is a critical part of the IVT increases with the input speed.

Synthesis and Analysis of a Parallel-Type Independently Controllable Transmission Mechanism

This study proposes an innovative transmission mechanism, called parallel-type independently controllable transmission (ICT). The proposed mechanism can provide functions similar to those of infinitely variable transmission (IVT) or continuously variable transmission (CVT) mechanisms. The parallel-type ICT can transmit rotational output speed that can be independently regulated using a controller and is unaffected by the speed variation of the input shaft. Thus, a variable speed wind turbine can generate electricity with a constant frequency and improved quality. The kinematic characteristics, torque distribution, and power flow of this transmission mechanism were verified using a prototype of the ICT to demonstrate the feasibility of its application.

Design, Modeling, and Experimental Validation of a Novel Infinitely Variable Transmission Based on Scotch Yoke Systems

A novel infinitely variable transmission (IVT) based on scotch yoke systems is designed to provide a continuously varied output-to-input speed ratio from zero to a specified value. By changing the crank length of scotch yoke systems, the speed ratio of the IVT can be continuously adjusted. The IVT consists of a pair of noncircular gears and two modules: an input-control module and a motion conversion module. The input-control module employs two planetary gear sets to combine the input speed of the IVT with the control speed from the stepper motor that changes the crank length of scotch yoke systems. The motion conversion module employs two scotch yoke systems to convert the combined speeds from the input-control module to translational speeds of yokes, and the translational speeds are converted to output speeds through rack–pinions. The speed ratio between the output of the motion conversion module and the input of the input-control module has a shape of a sinusoidal-like wave, which generates instantaneous variations. Use of scotch yoke systems provides a benefit to isolate the interaction between the crank length and the shape of the speed ratio, and a pair of noncircular gears can be used to eliminate the instantaneous variations of the speed ratio for all crank lengths. A prototype of the IVT was built and instrumented, and its kinematic behavior was experimentally validated. A driving test was conducted to examine the performance of the IVT.

An Innovative Design of Artificial Knee Joint Actuator With Energy Recovery Capabilities

The actuation systems of lower limbs exoskeletons have been extensively investigated and, presently, a great effort is aimed at reducing the weight and improving the efficiency, thus increasing the operating range for battery-operated devices. In this work, an innovative and more efficient actuation system to power the knee joint is proposed. The key and nonconventional elements of this alternative design are a flywheel and a micro infinitely variable transmission (IVT). This particular powertrain configuration permits to exploit efficiently the dynamics of human locomotion, which offers the possibility to recover energy. By means of simulations of level ground walking and running, it is here demonstrated how storing energy in the flywheel permits to reduce the energy consumption and to downsize the electric motor.

Energy Consumption of a Battery Electric Vehicle with Infinitely Variable Transmission

Battery electric vehicles (BEVs) represent a possible sustainable solution for personal urban transportation. Presently, the most limiting characteristic of BEVs is their short range, mainly because of battery technology limitations. A proper design and control of the drivetrain, aimed at reducing the power losses and thus increasing BEV range, can contribute to make the electrification of urban transportation a convenient choice. This paper presents a simulation-based comparison of the energy efficiency performance of six drivetrain architectures for BEVs. Although many different drivetrain and transmission architectures have been proposed for BEVs, no literature was found regarding BEVs equipped with infinitely variable transmissions (IVTs). The analyzed drivetrain configurations are: single- (1G) and two-speed (2G) gear drives, half toroidal (HT) and full toroidal (FT) continuously variable transmissions (CVTs), and infinitely variable transmissions (IVTs) with two different types of internal power flow (IVT-I and IVT-II). An off-line procedure for determining the most efficient control action for each drivetrain configuration is proposed, which allows selecting the optimal speed ratio for each operating condition. The energy consumption of the BEVs is simulated along the UDC (Urban Driving Cycle) and Japanese 10-15 driving cycle, with a backward facing approach. In order to achieve the lowest energy consumption, a trade-off between high transmission efficiency and flexibility in terms of allowed speed ratios is required.

A method of optimal traction control for farm tractors with feedback of drive torque

Traction efficiency of farm tractors barely reaches 50% in field operations (Renius et al., 1985). On the other hand, modern trends in agriculture show growth of the global tractor markets and at the same time increased demands for greenhouse gas emission reduction as well as energy efficiency due to increasing fuel costs. Engine power of farm tractors is growing at 1.8 kW per year reaching today about 500 kW for the highest traction class machines. The problem of effective use of energy has become crucial. Existing slip control approaches for farm tractors do not fulfil this requirement due to fixed reference set-point. This paper suggests an optimal control scheme which extends a conventional slip controller with set-point optimisation based on assessment of soil conditions, namely, wheel-ground parameter estimation. The optimisation considers the traction efficiency and net traction ratio and adaptively adjusts the set-point under changing soil conditions. The proposed methodology can be mainly implemented in farm tractors equipped with hydraulic or electrical infinitely variable transmissions (IVT) with use of the drive torque feedback.