Drag Torque Prediction Model for the Wet Clutches

Reduction of drag torque in disengaged wet clutch is one of important potentials for vehicle transmission improvement. The flow of the oil film in clutch clearance is investigated. A three-dimension Navier-Stokes(N-S) equation based on laminar flow is presented to model the drag torque. Pressure and speed distribution in radial and circumferential directions are deduced. The theoretical analysis reveals that oil flow acceleration in radial direction caused by centrifugal force is the key reason for the shrinking of oil film as constant feeding flow rate. The peak drag torque occurs at the beginning of oil film shrinking. A variable is introduced to describe effective oil film area and drag torque after oil film shrinking is well evaluated with the variable. Under the working condition, tests were made to obtain drag torque curves at different clutch speed and oil viscosity. The tests confirm that simulation results agree with test data. The model performs well in the prediction of drag torque and lays a theoretical foundation to reduce it.

Relationship between coal size reduction and energy input in Hardgrove mill

Hardgrove grindability index （HGI） is an important indicator of coal grindability, and is one of the most important parameters to determine the capacity of coal pulverizer in power station. However, HGI is an empirical grindability index without linkages to any known physical parameters. To investigate the effect of energy input on the grinding in Hardgrove mill. a T20WN torque meter was installed on the shaft of a modified Hardgrove mill to record the torque driving the mill. Samples from four kinds of coals with HGI ranging from 36 to 72 were prepared according to the procedure of standard HGI test and ground in a modified Hardgrove mill at different revolutions. The relation of sample size reduction degree to specific comminution energy （Ecs） was studied with Shi-Kojovic model, The results show that Shi-Kojovic model predicted well the coal size reduction degree with Ecs in Hardgrove mill. The griadability index given by Shi-Kojovic model has a similar trend with HGI. The relation of sample size reduction degree to Ecs reveals that HGI has a non-linear relationship with effective specific energy in Hardgrove mill, which explains the non-linear relation of HG1 to industrial pulverizer capacity.

A new calculation model of cutterhead torque and investigation of its influencing factors

Cutterhead torque is a crucial parameter for the design and operation of earth pressure balance （EPB） shield tunneling machine. However, the traditional calculation models of cutterhead torque are too rough or exist gross errors under variable geological conditions. In order to improve the precision of the calculation model of cutterhead torque, dynamic operation parameters are considered and a new model is proposed. Experiment is carried out on a ~1.8 m shield machine test rig and the calculating re- sult with the new model is compared with the experimental data to verify the validity of the new model. The relative error of the new model is as low as 4% at smooth stage and is reduced to 5% at the end of trembling stage. Based on the results of the new model and the test data obtained from the 001.8 m test rig and the construction site, the inner relationships between several operation parameters and cutterhead torque are investigated and some quantitative conclusions are obtained.

Continuous Estimation of Wrist Torque from Surface EMG Signals Using Path-dependent Model

Continuous estimation of wrist torque from surface electromyography(EMG) signals has been studied by some research institutes. Hysteresis effect is a phenomenon in EMG force relationship. In this work, a path-dependent model based on hysteresis effect was used for continuously estimating wrist torque from surface EMG signals. The surface EMG signals of the flexor carpi ulnaris(FCU) and extensor carpi radialis(ECR) were collected along with wrist torque of flexion/extension degree-of-freedom. EMG signal of FCU was used to estimate the torque of wrist flexion and EMG signal of ECR to estimate the torque of wrist extension. The existence of hysteresis effect has been proven either during wrist flexion or extension on all subjects.And the estimation performance of path-dependent model is much better than the overall model. Thus, the path-dependent model is suitable to improve the wrist torque's estimation accuracy.