Browse Topic: Continuously variable transmissions
ABSTRACT The HMPT500-3 is a split torque path hydrostatic / mechanical continuously variable transmission used in the Bradley Fighting Vehicle. Power transmission and steering is accomplished through the interaction of six planetary gear sets and two variable displacement hydrostatic pump / motor units (HSUs). Power flow in the HMPT500-3 is extremely complex, with numerous feedback paths within the planetary gear train. Without a clearly defined power flow path from gear set to gear set, the analysis cannot be handled in the conventional stepwise manner. The complete speed and torque equation sets must be solved simultaneously for all components. A linear algebraic approach was developed to model forward operation of the HMPT500-3 without steering. The left and right HSUs are lumped in a single unit, and the steering differential is ignored. A reduced set of 14 simultaneous equations for speed and 14 simultaneous equations for torque enable modeling of the ideal (lossless) power flow
Due to the compact structure of the Bacha Racing vehicle, the continuously variable transmission (CVT) serves as a crucial transmission component. It is essential to tune and verify its performance to ensure the power matching and transmission efficiency of the entire vehicle. This paper conducts a kinematic analysis of CVT based on transmission theory, designs real vehicle traction experiments, and CVT bench tests. Additionally, it proposes a method to utilize Hall sensors for real-time monitoring of CVT motion to assist in its tuning. The results demonstrate that the optimal performance tuning of the CVT for the Bacha Racing vehicle has been achieved through various experiments
This article presents an original methodology for the multi-objective optimization of Continuously Variable Transmission (CVT) for a wind turbine (WT). The objective functions of this optimization problem are to minimize the weight and maximize efficiency. This methodology also considers the variations of parameters caused by different factors (manufacturing tolerance, uncertainties in the operating conditions). Using a probabilistic model, the proposed algorithm combines a propagation of uncertainties and an optimization of the function objectives. The optimization is performed using the Non-dominated Sorting Genetic Algorithm (NSGA-II) with the advantage of exploring the global design space and finding the best compromise between the objectives. In order to verify the solution obtained by this approach, results were compared to the ones obtained by a previous study
An all-terrain vehicle (ATV) is capable of traveling on any kind of surface or terrain. It is built especially for extreme road conditions. High ground clearance and soft suspension springs are some of the characteristics of an ATV. The use of a four-wheel-drive (4WD) transmission in a light ATV is in high demand. Power on all four tires provides better traction and increases the off-roading capabilities of the ATV. The methodology described in the paper discusses the design and validation of a four-wheel driveline for a light ATV using various modeling and simulation software. Briggs and Stratton engine is coupled with a continuously variable transmission (CVT) to provide infinite ratios within its tuned range to deliver effortless shifting. A two-stage reduction gearbox is used to multiply the torque received from the CVT to provide sufficient traction to the tires. Power is transferred to the front differential via a propeller shaft. A shifting mechanism is installed for shifting
Hydrostatic torque modulation is a new, at moment theoretical approach, to developing advanced AWD4WD transmissions. The basic component is a rotational hydrostatic modulator. It is derived from a low-speed high-torque hydrostatic machine. As such, it can be integrated into a standard mechanical AWD4WD transmission as a replacement for the clutch, where torque is controlled through energy dissipation. Controlled by a simple solenoid valve, it provides torque vectoring with a reaction time shorter than 0.5 s, and it provides additional safety features that result in a more robust AWD4WD transmission. As it can modulate torque with energy flow control/transfer, it offers much more than existing systems based on controlled clutches. Specifically, hydrostatic torque modulation, when it is integrated into the AWD4WD transmission, brings CVT or ICT performance. As torque modulation is performed through the control of the energy flow, it provides torque control from 0 km/h without using a
This SAE Aerospace Recommended Practice (ARP) outlines the design and performance requirements for a battery-powered electric tow tractor for the handling of baggage or cargo trailers in airline service. The use of “shall” in this document indicates a mandatory requirement. The use of “should” indicates a recommendation or that which is advised but not required
The Continuously Variable Transmission (CVT) is a popular form of automotive transmission that uses friction between a belt and pulley to transmit power. Due to the sliding and other losses associated with the belt, power is lost in the form of heat, which must be dissipated to enhance the belt’s life. The task of heat dissipation is, however, complicated by the use of a CVT casing, which serves to protect the transmission from mud, debris, etc. Consequently, the design of an optimum CVT casing for efficient cooling is a challenging task. Experimental approaches or 3D numerical simulation approaches to tackling such problems are either involved or time-consuming or both. This article discusses a novel and simplified strategy for optimizing a CVT casing for maximum heat removal, using computational fluid dynamics (CFD). The rotating pulleys are approximated as heated, rotating cylinders inside a two-dimensional flow domain of the casing. Transient CFD calculations are carried out on a
The Continuously Variable Transmission (CVT) is a widely adopted transmission system. The operation of a CVT is simple, but successfully foretelling the longitudinal motion of a vehicle that utilizes this transmission is sophisticated. As a result, different vehicles taking part in BAJA-SAE competitions were developed using various strategies to model the vehicle’s longitudinal dynamics and CVT operation. This article aims to provide a tool for obtaining a quantitative estimate of the longitudinal performance of a CVT equipped vehicle and for the selection of an optimal drive-train gear ratio for such a vehicle. To this end, this article proposes a novel, relatively simple, and reasonably accurate mathematical approach for modeling the longitudinal motion of a vehicle utilizing a CVT, which was developed by a novel integration of existing vehicle dynamics concepts. The proposed technique splits the longitudinal motion into three distinct phases - low ratio acceleration, shifting, and
Passenger utility vehicles like car, SUVs, MPVs are used in wide application all over the world. Luxuries are becoming essential features of product mix along with comfort and ergonomics. Customer desires best shift quality with emerging technologies like AT, DCT, CVT, etc. and every OEM is working hard to achieve it. It is very difficult to satisfy the customer desire because of diversities in demographics and geographic. Gear shift quality (GSQ) is very crucial touch point in overall drive feel of vehicle. It consist of various parameters like mode selection feel, precision, comfort, select Noise, etc. It demands tradeoff practices among various parameters as stated. In this paper, external mode selection system of automatic transmission is explained. Various contributing parameters are explained with practical design approach for detent profile, mode selection mechanism, cable & dampers, etc. Among various GSQ parameters, in-cabin noise occurred during mode selection is also one of
A new Cruise Control Algorithm (CCA) commanding the Internal Combustion Engine (ICE) and the Continuous Variable Transmission (CVT) of a 200 hp tractor was implemented on a Rapid Prototyping System (RPS) and successfully tested with an empty vehicle and with 16 t trailer from 0.5 to 50 kph. Low velocities required an extra controller and a good concept for transition to higher velocities
The following article aims to compare the performance parameters between a continuously variable transmission (CVT) and a 6-gear manual transmission. The manual transmission is a usual type of transmission system, consisting in a clutch and a transmission gearbox, containing a set of gears which, according to the coupling chosen, creates a reduction between the speed of the engine and the gearbox output. Meanwhile, the continuously variable transmission (CVT) is a type of transmission that outputs any reduction, between certain limits, in a continuous way, from two pulleys linked through a metallic belt. Due to the characteristics of both transmission systems, it is possible to infer that there are differences on the vehicle’s performance. The comparison between both types of transmissions, applied to a passenger’s vehicle is done through the mathematical modeling considering the same usage profile. Thus, parameters such as vehicle speed, traveled distance, engine speed and
In order to improve the mode switching performance of parallel hybrid electric vehicles (PHEV) and make better use of the dynamics of the vehicle, this paper proposes a three-stage control method for the start-up mode of start-up, speed synchronization, and clutch slip based on the response characteristics of actual vehicle components and the complex working conditions of the actual road. In the speed synchronization phase, a coordinated control method of “engine speed active following + continuously variable transmission (CVT) speed ratio motor speed limiting” is proposed. The real vehicle test results show that the engine starting-up coordinated control method can significantly accelerate the speed synchronization and shorten the starting-up mode duration during the rapid acceleration, so that the vehicle’s power performance can be well played and the ride comfort can be effectively guaranteed
Baja SAE is an intercollegiate competition where teams design and build a single-seat off-road vehicle that is powered by a 10 HP Briggs & Stratton engine. Due to this power constraint, it is crucial to optimize the vehicle’s weight and performance. The design process began by creating a vehicle dynamics simulation, which included engine performance, continuously variable transmission (CVT) shifting, tire slipping, vehicle mass, rotational inertia, air drag, rolling resistance, weight shift, and drivetrain efficiency. These calculations predicted the time to reach 100 ft and the top speed for various gear box ratios to aid in gear ratio selection. The rotational inertia of the drivetrain is 40% of the total effective mass of the vehicle when the CVT primary is engaged and 12% when the CVT has fully shifted into a numerically lower gear, with the largest contribution coming from the inertia of the CVT primary pulley. A sensitivity analysis showed that the vehicle mass and coefficient of
This research paper concentrates on BAJA ATV CVT premises thermal cooling. BAJA event has a 4-hour endurance run, which demands full potential from the drivetrain. In our drive train assembly, we have used CVT coupled with fixed reduction gearbox, while having long run the temperature of CVT unit increases so much that it hinders the efficiency. The main heat generation sources in the CVT chamber is the engine, friction between belt and sheaves, and high ambient outside. It is learned that CVT working temperature should be reduced. Hence cooling was much required for optimum performance of our vehicle, implemented cooling system involves insulation of CVT from engine while having a passive heat exchanger using super absorbent polymer inside our vehicle to inject cool air on CVT and using insulating material on CVT cover to reduce the overall temperature, whereas passive heat exchanger cools down the injected air. All this leads to significant temperature drop in whole assembly
The RADIALcvt is a traction drive continuously variable transmission (CVT) implemented in a new novel radial configuration mechanical assembly. The RADIALcvt functions as a multi-parallel power path (at least six) type of CVT, which consists of only one steel-on-steel, line contact, traction drive interface in each power path. A constant input radius on the traction drive input makes it possible to use a constant clamping force, which is provided by mechanical springs, thus eliminating the need for a hydraulic control system. The RADIALcvt has a very large radius variation on the traction drive output, which provides the ratio variation. The test and simulation results of the first RADIALcvt prototype was published in [1] and presented mechanical efficiencies above 90%. This article presents the simulation and test results of the second-generation RADIALcvt prototype, which presents mechanical efficiencies above 94% and includes measured parameters of mechanical efficiency, slip
This study aims to solve the problem of impact in a parallel hybrid electric system based on the continuously variable transmission (CVT) during switching from pure electric mode to engine-driven, power-generating mode. Taking into account the torque response characteristics of the engine and motor and the dynamic characteristics of the wet clutch hydraulic control system, the mode switching process is divided into six stages, namely, pure electric mode, wet-clutch free travel, engine start-up, engine speed synchronization, clutch combination, and engine intervention drive. A coordination control strategy is developed based on the model predictive control algorithm to ensure smooth mode switching. The effectiveness of the control algorithm is verified using Matlab/Simulink and the AMESim co-simulation platform. Results show that with the mode switching coordination control strategy, the components of the system work harmoniously. The maximum impact is reduced by 52.0% at the speed
This SAE Recommended Practice establishes the test procedure, environment, and instrumentation for determining the maximum sound level potential for motorcycles under wide open throttle acceleration and closed throttle deceleration
This SAE Standard is equivalent to ISO 362-1:2015 and specifies an engineering method for measuring the noise emitted by road vehicles of categories M and N under typical urban traffic conditions. It excludes vehicles of category L1, L2, L3, L4, and L5. The specifications are intended to reproduce the level of noise generated by the principal noise sources during normal driving in urban traffic. The method is designed to meet the requirements of simplicity as far as they are consistent with reproducibility of results under the operating conditions of the vehicle. The test method requires an acoustical environment that is obtained only in an extensive open space. Such conditions are usually provided for during: Measurements of vehicles for regulatory certification and/or type approval. Measurements at the manufacturing stage. Measurements at official testing stations
When the belt contacts a pulley in a pushing belt-type CVT, vibration is generated by frictional force due to rubbing between the individual elements that are components of the belt, which is said to increase wear and noise. The authors speculated that the source of that vibration is misalignment of the secondary pulley and primary pulley V-surfaces. To verify that phenomenon, a newly developed micro data logger was attached to an element of a mass-produced metal pushing V-belt CVT and the acceleration was measured at rotations equal to those at drive (1000 to 2500 r/m). In addition, the results of calculations using a behavior analysis model showed that changes in pulley misalignment influence element vibration, and that the magnitude of the vibration is correlated to the change in the metal pushing V-belt alignment immediately before the element contacts the pulley
The following schematic diagrams reflect various methods of illustrating automotive transmission arrangements. These have been developed to facilitate a clear understanding of the functional interrelations of the gearing, clutches, hydrodynamic drive unit, and other transmission components. Two variations of transmission diagrams are used: in neutral (clutches not applied), and in gear. For illustrative purposes, some typical transmissions are shown
In order to improve the performance of electro-hydraulic composite braking system of hybrid electric vehicle (HEV), a new type of plug-in HEV with dual motor was taken as the research object. The model of motor loss was built to achieve maximum motor efficiency, and the hydraulic braking system model, which can dynamically control pressure, was built. Based on the optimization of a motor’s continuously variable transmission (CVT) joint efficiency, the real-time optimal allocation strategy based on threshold method and cooperative control strategy of the electro-hydraulic composite braking system were brought out to recover most of the regenerative energy under the premise of ensuring safety. The model was built to verify the performance by AMESim-Simulink. The results show that the control strategy can take the advantages of dual-motor braking recovery system, increase braking energy recovery rate, effectively improve the braking safety and ride comfort of the vehicle, and reduce
Technological and commercial development of vehicles specifically conceived for urban use would certainly be a crucial aspect in making mobility sustainable in urban contexts thanks to their limited in size and low fuel consumption and emissions. Hybrid drive trains are particularly suited to this purpose: if properly designed, very small-sized thermal engines can give all the energy and power required for the application, also making pure electric driving possible when required. The authors are involved since a decade in proposing new low-cost solutions to address this market sector. Market itself explored these possibilities and nowadays offers some BEV solutions in this market share, but it is still lacking in proposing solutions for a parallel full hybrid drive. The main reason must be searched in the complexity of normally applied parallel-hybrid propulsion systems which is not compatible with the limited costs of the application. Taking the lead from these considerations, the
The RADIALcvt is a traction drive continuously variable transmission (CVT) implemented in a new novel radial configuration mechanical assembly. The RADIALcvt functions as a multi-parallel power path (at least six) type of CVT, which consists of only one steel-on-steel, line contact, traction drive interface in each power path. A constant input radius on the traction drive input makes it possible to use a constant clamping force which is provided by mechanical springs, thus eliminating the need for a hydraulic control system. The RADIALcvt has a very large radius variation on the traction drive output which provides the ratio variation. The fact that the RADIALcvt input traction rollers are clamped between two opposite rotating disks results in a clamping force which is about 50% of the equivalent clamping force of a typical traction drive CVT. This paper presents the basic mechanical configuration of the first prototype, a traction drive simulation as well as the test results of the
Items per page:
50
1 – 50 of 651