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1、Model validation of the output reciprocating dynamic responses of a twin electro-rheological (ER) clutch mechanismK.P. Tan *, A.R. Johnson, R. Stanway, W.A. BulloughDepartment of Mechanical Engineering, University of Sheffield, Mappin Building, Mappin Street, UKReceived 2 November 2005; received in
2、revised form 24 April 2006; accepted 10 December 2006 Available online 5 February 2007AbstractElectro-rheological (ER) fluid devices are becoming more popular in the industrial applications. This is due to the fast speed of response and large output dynamics of the ER actuators. The usefulness of th
3、is ER dynamic response is considered in the material winding processes where fast output bi-directional responses are essential. Therefore in the present paper, an ER twin clutch mechanism is proposed. This clutch mechanism consists of two identical clutches that rotate in opposite directions. But t
4、he bi-directional output dynamics of the clutch mechanism is not well understood due to its non-validation in the past. The main aim of this paper is to model the reciprocating responses of the clutch mechanism and then perform model validation with the measured test results. The close agreements be
5、tween the modeled and experimental data indicate that the ER output angular velocity and displacement responses models of the clutch mechanism are validated. These validated models can then be used to predict accurately the reciprocating output responses of the twin ER clutch mechanism for future re
6、search studies. 2007 Elsevier Ltd. All rights reserved.Keywords: Electro-rheological; Twin clutch mechanism; Bi-directional; Model validation; ER angular velocity; Displacement responses1. IntroductionIndustrial applications such as the yarn production in the textile industry and the winding of fila
7、ments onto bobbins normally require actuators that can provide fast reciprocating speeds of responses and large output torques. To resolve this issue, various devices are considered. The present servomotors are unsuitable in this application due to their cogging torque responses and large output ine
8、rtia 16. Next, the smart fluid actuators are considered. By using the electro-rheological (ER) fluid as the working medium, an ER clutch can be a potential rotary device. This analysis is obtained by considering the following research investigations. In the past, Carlson et al. 7, Firoozian et al. 8
9、 and Tan et al. 9 tested the ER clutch and they reported the ER fast speed of response and huge dynamic responses. Next, Johnson et al. 10 and Bullough et al. 11 employed inertia loadings at the output shaft of the ER clutch. The pick-up and drop-load velocity responses deliveredCorresponding author
10、.E-mail address: alpha elderyahoo.co.uk (K.P. Tan).0094-114X/S - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.mechmachtheory.2006.12.0051548K.P. Tan et al. / Mechanism and Machine Theory 42 (2007) 15471562by the ER clutch were significantly fast in terms of tens of millisec
11、onds. These fascinating ER dynamics motivated Brookfield and Dlodlo 12,13. They employed a proportional-integral-derivative (PID) controller to activate the ER clutch for driving a robot arm to reach a robotic positioning error of 0.75. A limitation of their ER application is that the inertia arm wa
12、s driven at fast speed of response in one direction. Therefore to achieve fast bi-directional responses, the following ER research works are considered.In order to actuate the inertia loads in both directions, Choi et al. 14 used an ER clutch-brake mechanism to achieve start-stop motion responses. A
13、lthough this clutch-brake mechanism could perform bi-directional responses, but the turn-round dynamics or reciprocating dynamics were slow. Therefore for the purpose of actuating the output inertia at fast speed of response in the forward and reversal motions, the authors studied a twin ER clutch m
14、echanism 15-17. This clutch mechanism consists of two identical clutches that are driven by their respective electric motors to rotate in different directions. In the working process, one of the energized rotary ER clutches actuates the output inertias to travel in one direction when the other clutc
15、h is non-energized. To generate reciprocating responses on the inertias, both the clutches are activated alternately by the electric fields. But, there is no detailed understanding of the bi-directional response of this clutch mechanism particularly on the ER speeds of responses or turn-round dynami
16、cs of the inertias. Therefore in this present paper, two mathematical models are derived to understand the output angular velocity and displacement responses of the reciprocating clutch mechanism. To prove its validity, these kinematic models of the clutch mechanism undergo validations with the expe
17、rimental ER output angular velocity and displacement responses. This validation work is necessary due to it can provide key knowledge on the reciprocating dynamics of the smart actuators. Next, the authors describe the organization of this paper as follows.Section 2 describes the test facility of th
18、e clutch mechanism. Section 3 illustrates the derivations of the mathematical models for the ER output angular velocity and displacement behaviors. Section 4 validates these models by using the measured kinematic responses of the ER clutch mechanism. Section 5 is the respective conclusion. Appendix
19、1 tabulates the measured results of the ER torque and passive fluid viscosities.2. The reciprocating twin ER clutch mechanismFig. 1 is the overall mechanical assembly of the ER clutch mechanism. In this clutch mechanism, two identical co-axial ER clutches are arranged vertically. The detailed assemb
20、ly of each ER clutch is presented in Fig. 2. Section 2.1 describes the mechanical assembly of the twin clutch mechanism. Section 2.2 presents the electrical facility that is used to energize the ER fluid clutches alternately. Section 2.3 is a detailed description of the ER reciprocating process in t
21、he clutch mechanism.2.1. Description of the mechanical arrangement of the twin ER clutch mechanismIn Fig. 2, the two fundamental components of the co-axial ER clutch are its input rotor (1) and output rotor (2). The former rotor is the ground potential electrode and the latter rotor is the high volt
22、age electrode. Both these rotors are made of stainless steel. The input rotor has outer and inner diameters of 52 mm and46 mm, respectively. The ER active external and internal diameters of the output rotor are 51mm and47 mm, respectively. When coupled together, both these rotors have ER active leng
23、ths of 30 mm across two inter-electrode gap sizes of 0.5 mm each. Due to the embedded ER fluid between both the electrode gaps, the viscous active inner and outer lengths of the output rotors are 30 and 40 mm, respectively. After the descriptions of both the rotors, the mechanical assembly of the tw
24、in ER clutch mechanism is stated below.The output rotor of the ER clutch is assembled to a mild steel shaft (3) by means of two ball bearings. This shaft is then engaged to the input rotor co-axially using a key and keyway. This forms a sub-assembly of the ER clutch. Next, each of the two sub-assemb
25、lies is coupled tightly to a mild steel column by employing two ball bearings and a locknut. Each ER clutch-column assembly is fitted rigidly to a high voltage isolator (4). The latter is placed between an AC motor and the clutch-column assembly. This isolator serves to protect the electrical circui
26、try of the AC motor from the effects of the high voltages that are applied to the clutch. Two isolators are placed below the twin clutch-column assemblies. The AC motor is described as follows.The employed motor is a 3 phases, AC induction type (Electrodrives Limited, serial number: BH114203). For t
27、his motor, it can deliver a maximum mechanical power and an angular speed of 0.25 kW and 2800 rpm,K.P. Tan et al. / Mechanism and Machine Theory 42 (2007) 154715621549DC tachoneterThis enclosed section is enlarged and labeled as shown in Figure 2.DC tachoneter0175 nrFig. 1. Physical arrangement of t
28、he twin ER clutch mechanism.respectively. Since each of the ER clutches is driven by the output shaft of the motor (5), two identical AC induction motors are employed. They are arranged in vertical positions with a horizontal distance of 0.175 m apart as shown in Fig. 1. By using a manual speed regu
29、lator, the motors are controlled to spin at similar output rotational speeds but in the opposite angular directions. This implies that the left and right motors undergo clockwise and anti-clockwise rotations respectively. In order to integrate these motor dynamics into the overall performances of th
30、e clutches, the following tasks are performed.By using its output shaft (5) and an Oldham coupling (6), each of these motors transmits its output dynamics to the respective coupled clutch. However prior to the clutch rotation, a nylon cover and an O-ring rubber seal (7) are used to seal the ER fluid
31、 (8) securely within each clutch compartment. Then, a nylon, spur type, gear wheel (9) of 80 mm pitch circle diameter and 125 external gear teeth is tightened rigidly to the output rotor of each ER clutch. For the sub-assembly of each clutch, the total output moment of inertia is 3.83 x 10 kgm inclu
32、sive of its attached gear wheel. Next, the twin clutch-column assemblies are coupled with the two motors. Finally, a toothed timing belt (13) of 16 g mass and 630 mm in length is engaged with the external gear teeth of the two gear wheels. The gear wheels and timing belt are used to integrate the ro
33、tational dynamics of the output rotors of both the ER clutches. Next in order to achieve reciprocating output responses of this clutch mechanism, the following facilities are described.2.2. Description of the electrical facilities for the ER reciprocating responsesFor the purpose of activating the E
34、R clutches electrically, three sets of connections are required. Initially, two carbon brushes are used to contact the output rotors of the ER clutches. Then, two output probes from the EHT switch boxes are fitted firmly to the carbon brushes. This is to link the high voltage supply to the clutches.
35、 The source of these probes originates from the electrical circuitry as shown in Fig. 3. Next, two carbon1550K.P. Tan et al. / Mechanism and Machine Theory 42 (2007) 15471562100 nnFig. 2. Enlargement view of enclosed ER clutch section from Fig. 1. Key: 1. input rotor; 2. output rotor; 3. shaft; 4. H
36、V isolator; 5. drive shaft of the electric motor; 6. Oldham coupling; 7. nylon cover and O-ring seal; 8. ER fluid; 9. gear wheel; 10. carbon brushes; 11. stand; 12. ball bearing; 13. belt.Farnellpowersupply o carbon brushes of ER clutch Ah unction GeneratorMutplexerJ SwtchCurrent Measurement UntTo c
37、arbon brushes of ER clutch B100 MegaohmsKSM high voltage power supplyER Current (Channel 3)ni-Inar(Channel 2)lote: IE: nternal earthCE: common earthFig. 3. Electrical circuitry for the twin ER clutch mechanism.probes contact the external surfaces of the two input rotors to form the earth connection.
38、 Thus, the electrical path of the twin clutch mechanism is completed.K.P. Tan et al. / Mechanism and Machine Theory 42 (2007) 154715621551In Fig. 3, the detailed descriptions of the KSM power supply, Farnell function generator, voltage and current measurement units, LeCroy oscilloscope, Farnell powe
39、r supply and EHT switch boxes 18,19 had been stated previously. Similar descriptions had been given for the tested ER fluids of Lipol L30155, L40155 and Bayer AI3565 50% volume fraction fluids. Their volume fractions are 30%, 40% and 50% respectively. The temperature ranges of these ER fluids are be
40、tween 0 C and 80 C. The largest electric field strength inputted to all these ER fluids is 5 kV/mm. These ER fluids (8) fill the ER clutch compartment as shown in Fig. 2. In order to activate the fluid clutches with the electrical facilities of Fig. 3, the output high voltage waveform of Fig. 4 is e
41、mployed.The usage of the above bi-polar voltages is to fulfill two main aims. The first aim is to energize one ER clutch and de-activate the other clutch in order to achieve belt reciprocating response. However, the main objective of switching the polarity differences is to prevent the occurrence of
42、 electrophoresis of the tested ER fluid. This electrophoresis can breakdown the ER effect and it produces inaccurate output dynamic results 19. By applying the above bi-polar voltages to the twin ER clutch mechanism in Fig. 1, the belt traverses with linear reciprocating motion. This ER reciprocatin
43、g output dynamics are next described as follows.2.3. Description of the ER reciprocating process in the twin clutch mechanismIn this section, the ER reciprocating dynamics are described by means of the key positions of the reciprocating belt as shown in Fig. 5. The mid and two extreme positions on t
44、he belt are points 0/5, 3 and 8, respectively. These two end points are produced due to the fast speeds of response of the ER clutches during their individual bi-polar, on-off energisations and passive slippages. In order to understand the belts dynamics from points 0 to 9, Table 1 shows the behavio
45、r of the output angular velocity responses of the two ER clutches, states of energisations and slippages at different belt positions. The term Energisation is defined+ hv+ HV0 V0 V II 0 V0 V I HV(Left hand side ER clutch or clutch A)- HV0 V+ HV+ H V0 V0 VHV(Right hand side ER clutch or clutch B)Fig.
46、 4. Waveforms of bi-polar high voltage applied to energize the two ER clutches. (HV is high voltage, + is positive polarity and is negative polarity.)point where angular dsplacementand angular velocity ofoutput rotor are measuredLeft hand /Right hand clutch2 3Fig. 5. Plan view of twin clutch mechani
47、sm for describing the engagement or slipping behavior of the ER clutches A and B during a complete belt traversing cycle.1552K.P. Tan et al. / Mechanism and Machine Theory 42 (2007) 15471562Table 1Key to the positions marked on the belt in Fig. 6Positions of belt motionOutput rotor velocity response
48、ER Clutch AER Clutch BEnergiseSlippage YesEnergise YesSlippage0 to 1 constant speed-QNoNo1 voltage A on, B off-QYesYesNoNo1 to 2-QYesYesNoYes2 ER torque A on0 co 0YesYesNoYes2 to 3 decelerating0 co 0YesYesNoYes3 stopped0YesYesNoYes3 to 4 accelerating0 co 0YesYesNoYes4 to 6 constant speedQYesNoNoYes6 voltage A off, B onQNoN
