Global Performance Index Research Articles

A method to calculate a global performance index for materials. An application to thermoplastic polymers

More and more frequently, different materials have to be compared to find out the most suitable for a specific use. A large number of individual properties and performances have to be considered at the same time and a synthetic evaluation via a global performance index (GPI) may be very useful. In this paper, a new methodology, previously used for durable goods, is applied for the first time to polymeric materials. The GPI can be obtained, starting from basic parameters expressing the performance of each material considered, through the construction of a ‘relevance tree’ with increasing level of data aggregation. The construction can be performed either graphically or algebraically by using nomograms or a computer implemented algorithm, respectively. In the latter case, the influence of the averaging functions over the final GPI is also discussed.

A Global Performance Index for the Kinematic Optimization of Robotic Manipulators

In this paper, a novel performance index for the kinematic optimization of robotic manipulators is presented. The index is based on the condition number of the Jacobian matrix of the manipulator, which is known to be a measure of the amplification of the errors due to the kinematic and static transformations between the joint and Cartesian spaces. Moreover, the index proposed here, termed global conditioning index (CGI), is meant to assess the distribution of the aforementioned condition number over the whole workspace. Furthermore, the concept of a global index is applicable to other local kinematic or dynamic indices. The index introduced here is applied to a simple serial two-link manipulator, to a spherical three-degree-of-freedom serial wrist, and to three-degree-of-freedom parallel planar and spherical manipulators. Results of the optimization of these manipulators, based on the GCI, are included.

The elaboration of global performance indices for evaluating durable goods

This paper proposes a method which allows us to arrive at a global performance index (GPI) for durable goods such as automobiles, industrial vehicles, aircraft, farm machinery, electric household appliances and air conditioners. The procedure consists of determining (for each separate category of product) the property and performance factors requisite to an evaluation of the concrete qualitative efficiency of such goods. Clearly, it must also be possible to measure and to reproduce such properties on a world- wide scale. Then, intermediate performance indices must be obtained, and the pre-established properties logically paired off with these. This can be done by means of nomograms. The subsequent matching-up of the intermediate indices leads to a global index which is useful for carrying out comparisons and economic evaluations.

A correction procedure for separating direct and diffuse insolation on a horizontal surface

Knowledge on the diffuse horizontal irradiance (DHI), and direct normal irradiance (DNI) is crucial for the estimation of the irradiance on tilted surfaces, which in turn is critical for photovoltaic (PV) applications and for designing and simulating concentrated solar power (CSP) plants. Since global horizontal irradiance (GHI) is the most commonly measured solar radiation variable, it is advantageous for establishing a suitable method that uses it to compute DHI and DNI. In this way, a new model for predicting the diffuse fraction (Kd) based on the climate zone is proposed, using only the clearness index (Kt) as the predictor and 1-min resolution GHI data. A review of the literature on models that use hourly and sub-hourly Kt values to compute Kd was also carried out, and an extensive performance assessment of both the proposed model and the models from the literature was conducted using ten statistical indicators and a global performance index (GPI). A set of model parameters was determined for each climate zone considered in this study (arid, high albedo, temperate and tropical) using 48 worldwide radiometric stations. It was found that the best overall performing model was the model proposed in this work.