Development a test rig in order to measure the mechanical dissipation of torque and measures

It is becoming increasingly more important to design washing machines consuming less energy and water. Furthermore, customers are demanding these machines to have more laundry capacity, to be economic and producing less noise. Consequently, washing machine producers are trying to come up with solutions to satisfy customer demands so as to survive in a competitive environment. In order to reduce energy consumption, improvements need to be made specifically on components within the excitation group (seal, ball bearing, electromotor, silencer, drum pattern). There are different variations for each component in the excitation group. It is well known that, it will be too costly to use classical product development methods based on designing, prototyping and testing prototypes for all possible combinations. Therefore, a special test rig is required, which will enable easy assembly and disassembly for electromotor and components within the excitation group. As the test rig needs to represent the dynamics of a washing machine, this test rig needs to be designed using the state-of-the-art design tools such as finite element method. In order to have realistic results, the dynamic behavior of the test rig should be quite similar to the dynamic behavior of the washing machine. Therefore, the fundamental characteristics of a washing machine are identified first using vibration tests. Natural frequencies of the excitation group (drum, tub, electric motor assembly) are determined experimentally. Then the finite element model of the washing machine is revised to make the natural frequencies predicted by the model as close as possible to the experimental values. Various details in the model of the test rig need to be included in order to bring the dynamic behaviour of the numerical model closer to that of the washing machine. Another criteria during the design of the test rig is that it should allow easy assembly and disassembly of the components as the tests to be done are numerous. The finite element model is used to simulate various possible design options. Various models are created, analysed and the mechanical components of the final design are produced and a test rig is built. Once the test rig is operational, some preliminary tests are carried out in order to validate the performance of the test rig. To do this, the torque requirement of a washing machine is measured using a torque meter installed on a washing machine first. Then the torque requirements of the test rig are also measured when similar components are used in the test rig. After getting very similar results from washing machine and test rig measurements, more detailed torque measurements using the test rig are carried out so as to establish the amount of torque requirement (or energy consumption) of the individual components of the washing machine. In order to do so, the ball bearing and the drum shaft are assembled first to determine the frictional torque caused by the ball bearings itself in the system. After that, other components are added to the system to measure the amount of additional frictional torque needed in the system. In other words, as more components are added to the system, the amount of frictional torque is increased relative to the previous case, difference being due to the added component. For each case, the measurements are repeated at least 10 times for averaging purposes. It is shown that the test rig developed is capable of measuring the frictional torque safely at steady state condition at constant speed using the torque meter. However, a special test procedure is developed in this thesis in order to obtain the frictional torque requirement as a function of rotational speed using the same test rig, but without the need for a torque meter. According to this procedure, the system is accelerated to the maximum rotational speed first. Then the belt between the electric motor and the pulley is removed and the rotational speed is measured until the system stops. A code is developed using by Matlab program. Frictional torque is then obtained by processing the angular speed as a function of time and the inertia of system using a Matlab code developed for this purpose. Following such tests, various combinations of components are tested so as to identify their contributions to the energy consumption of the washing machine. These measurements and the resulting suggestions allow for systematic minimization of the total energy consumption of the machine. The test rig developed in this thesis can also be used for quality control purposes.