Study On COT Types Of Automatic Transmission And Their Gearshifts Dynamics And Control

Transmission is one of the most important components in vehicles.It has played a crucial role not only in the gasoline vehicles,but also in the hybrid and pure electric vehicles.Lack of original patents,singleness of product types,and huge of limiting factors by manufactories abroad are the three main problems of China’s automatic transmission industry now.This paper presents a novel type of automatic transmission named Clutch and Overrunning Clutch Transmission(COT),based on research on typical automatic transmissions,such as AT,AMT,and DCT.Several different structure layouts of the COT are proposed by method of knowledge innovation,which is also presented in the paper.Some components in the COT are designed.A model of driveline based on the COT is built.Shift dynamics and control strategy are researched by Newton dynamic methods.Simulations and tests are carried out.Firstly,working principle and structure layouts of the COT are discussed.The working principle of the COT is that the torque transferred from the engine switches between friction clutch and one-way clutch.Shifts of all gears work in the same way.An innovation method using Knowledge Map and TRIZ theory is developed to manifold gear number and cut down Y length of the COT.Four types of structure layouts of the COT are found by the innovation method.Detail structure models of these four layouts are built to exam if the COT could be developed to be products.The results of model building show that the COT has ability to be products,and prove that the innovation method is availability to develop new types of automatic transmissions.Secondly,shift dynamic of the COT is studied.Dynamic model of driveline with the COT is built.Dynamic functions of both upshift and down shift are presented.Torque calculating models of several components are built,such as the Engine,the Wet Friction Clutch,Overrunning Clutch and Wheels.Timing logic of the control strategy of the COT for both upshift and down shift are built.Simulations based on the software of AMEsim are carried out.The results of the simulations of both up and down shifts show that the COT shifts directly,efficiently,and without traction interruption.Thirdly,method of impact of engagement of overrunning clutch on transmission is pre-sented.Dynamic models including steady states and transient state are built based on the second Newton’s law.The nonlinear torque of the engagement of the overrunning clutch is calculated using explicit FEM method.The torque of output shaft and rotational velocities of both input and output shaft are calculated under the excitation of torque of the input shaft and impact generated by quick engagement of the overunning clutch,which is obtained by explicit FEM method.Tests on the engagement of the overunning clutch during shifts are carried out.The test results show that the torque peaks and the vibration frequencies on the output shaft are similar in different situations when the speeds of input shaft are different.The simulation results are similar to the test results.This proves the method is appropriate to research the dynamic characters of the transmission shifting by overunning clutches.Fourthly,shift controller of the COT is developed.The shift controller is divided into tree level as a basic level,a middle level and a top level.Control strategy in the basic level is developed to control the components,such as clutches and synchronizers.Control strategy in the middle level is developed to control the working process of the transmission,such as shifts and launch.Control strategy in the top level is developed to control the working conditions of the transmission,such as upshifts and downshifts.The critical control steps are discussed during both upshift and downshift.The state functions are linearized to make shifts control be easier.The controller is developed by the control method of Fuzzy Sliding Mode.The sub-controllers,Fuzzy Controller and Sliding Mode Controller,are built respectively.Simulation of control system is carried out.The results of the simulation show that the controller of Fuzzy Sliding Mode could control the COT accurately and quickly.Finally,bench tests of working conditions of upshift and downshift of driveline with a 2-gear COT are carried out.Shift dynamic and shift control are the two parts of the tests.The test result of shift dynamic shows the COT shift directly and without traction interruption,which is corresponding to the simulation of the shift dynamic.The test result of shift control shows the Fuzzy Sliding Mode control method makes the COT shift smoothly and quickly,which is corresponding to the simulation of the shift control.The test results show the jerk of the COT during shift is not up to 10 rads-3,which is allowed by the standard provided by the transmission industry.The test results also show the calculation models built for shift dynamic and shift control are correct,and the control strategy is useful for the COT.As conclusion of this paper,the COT,a novel type of automatic transmission,is able to be developed to be products equipped in passenger cars.