Norman C. Otto

Vehicle vibration simulator

A vehicle vibration simulator to simulate occupant exposure to vibration in a motor vehicle includes a reaction mass, a seat portion, a seat actuator between the reaction mass and the seat portion for providing at least one degree of vibration freedom, a steering column portion, a steering column actuator between the reaction mass and the steering column portion for providing at least one degree of vibration freedom, a floorpan portion, a floorpan actuator between the reaction mass and the floorpan portion for providing one degree of vibration freedom, the seat actuator, steering column actuator and floorpan actuator being actuated independently and/or simultaneously to simulate occupant exposure to vehicle vibration.

MATHEMATICAL MODELS FOR CATALYTIC CONVERTER PERFORMANCE

Mathematical models which can aid in the design of monolithic oxidation catalyst systems are described. The chemistry math model allows prediction of tailpipe CO and HC emissions throughout the course of the Federal Test Procedure. Following a brief description of the model and its required inputs, several examples of model applications are presented.

Simulation of material delivery systems with dolly trains

Well designed material delivery systems should support the production systems with timely delivery of material from its point of arrival to the plant to its point of use. This paper describes a simulation methodology to model and capture the behavior of systems which use dollies to deliver material. The models evolved over time by modeling several real world applications in a variety of manufacturing facilities. As compared to forklift systems, modeling dolly delivery is much more complex and requires several special features. Crate, dolly, and train entities merge to model loading at the dock and split to model dropoff at the aisles. Data structures are used to transfer and maintain information across these different entities. Decision logic must also be added to model dolly selection, train routing, and alternative actions when resources are not available. New control entities must be used to control loading dollies from the floor and periodic collection of empty dollies. All these techniques are described in the paper along with the model flow logic traced from dock unloading to aisle and line feed delivery to return and reloading of empties on the truck. Application of the models to a JIT implementation at an assembly plant and to the manufacturing facility design problem are also presented.

Impulsive noise of printers: measurement metrics and their subjective correlation

In the office and home computing environments, printer impulsive noise has become a significant contributor to user perceived quality or lack thereof, and can affect the user’s comfort level and ability to concentrate. Understanding and quantifying meaningful metrics for printer impulsivity is becoming an increasingly important goal for printer manufacturers. Several methods exist in international standards for measuring the impulsivity of noise. For information technology equipment (ITE), the method for detection of impulsive noise is provided in ECMA‐74 and ISO 7779. However, there is a general acknowledgement that the current standard method of determining impulsivity by simply measuring A‐weighted sound pressure level (SPL) with the impulsive time weighting, I, applied is inadequate to characterize impulsive noise and ultimately to predict user satisfaction and acceptance. In recent years, there has been a variety of new measurement methods evaluated for impulsive noise for both environmental and mach...

Simulation models of material delivery systems

One important aspect of JIT (just-in-time) manufacturing is the timely delivery of material from its arrival point at the facility to the point of processing. A simulation modeling method which captures the essentials of this process is described. This method was developed through several applications to actual systems. These applications cannot be modeled by simple simulation modeling constructs. Specialized modeling logic and constructs for truck arrival and unloading, moving material to an intermediate storage area, reloading the truck with empty containers, and feeding the production lines are presented. Several applications are discussed and used to demonstrate the types of issues and problems these models are capable of addressing.<<ETX>>

The Design of Automotive Acoustic Environments: Using Subjective Methods to Improve Engine Sound Quality

The sensory environment of the vehicle is an area where customer expectations have greatly increased in recent years. For example, sound quality has become a very important factor in determining customer perception of vehicle quality and value. In this paper, a method for evaluating sound quality is presented and used in an engine design application. As part of the design of a future midsize vehicle, 14 engine component modifications were being considered as ways to improve sound quality. A subjective evaluation was carried out to determine if these modifications had any effect on perceived sound quality and, if so, which modifications provided the greatest sound quality benefit. A paired comparison method was used in which subjects judged, first, similarity and, then, preference. The similarity results showed that the vehicle sounds were indeed perceived quite differently. Additional analysis, using multidimensional scaling, revealed that most of these differences could be attributed to just three of the modifications (lightweight valvetrain, crankshaft counterweight, and accessory drive). The preference results confirmed that these three components also governed the valuative judgements. As a result of this study, these modified components were included in the final vehicle design. More generally, the subjective evaluation and analysis procedure described here offers a means for bringing human factors into the design of automotive acoustic environments.

Just‐noticeable differences in vertical vibration for seated subjects

Just‐noticeable differences in bandlimited vertical vibration were studied for subjects sitting on automotive seats. Stimuli consisted of octave band frozen Gaussian noise centered at 4, 8, and 16 Hz. Two‐interval forced‐choice paired comparisons were used, with a reference level of 8 mg. The level of the alternative stimulus in the pairs varied from 8.25 to 10 mg. Stimulus intensity was measured with a seat pad accelerometer. Stimulus durations of 4 s plus 1/2‐s tapers were used for all frequency bands, with 1/2 s between stimuli. Sets of trials with 2‐s durations at 16 Hz were done as a test of duration effects. Three subjects were trained with feedback until performance stabilized. Then 200–250 trials were performed in blocks of 25 or 50 for each of four alternatives at each frequency and each subject. Thresholds determined from the psychometric functions ranged from 0.6 to 1.8 mg, with most between 0.6 and 1.2. Little frequency dependence was evidenced over all frequency bands, and little duration eff...

A model for predicting roughness of powertrain sound.

The semantic dimension of rough/smooth can be an important factor in customer preference of automotive powertrain sound. With this in mind, a new model is proposed for predicting roughness of powertrain sound. The model performs a signal decomposition into critical bandwidth channels, specific roughness prediction for each channel, and a combination of specific roughness across frequency to yield an overall roughness measure. Signal decomposition is performed with a bank of overlapped, critical bandwidth, bandpass filters. Because the signal in each channel is well represented by a small number of harmonically related, narrow‐band components, it is assumed that specific roughness can be determined from the peaks in the magnitude spectrum of the envelope signal. A masked threshold estimate from the input signal is used to predict audibility of envelope fluctuation in each filterbank channel. Channels whose envelope fluctuation falls below threshold are assumed not to contribute to overall roughness, and ar...

Identification and characterization of automotive powertrain sound quality attributes

As vehicle interior noise levels decrease and customer expectations of comfort increase, measures of sound‐pressure level are no longer sufficient to characterize the acoustic environment of the vehicle. It therefore becomes important to study other sound attributes that affect customer satisfaction. A procedure has been developed by which customers identify and evaluate the important powertrain attributes, using the semantic differential technique. The attributes fall into two categories, psychoacoustic (loudness, roughness, pitch) and ‘‘halo’’ (expensive, reliable, powerful). By correlating the semantic result with preference data, it can be determined which attributes contribute most to customer preferences. Attributes important for one market segment may be unimportant for another segment. The semantic differential results are correlated to objective sound quality metrics. Comparison of the results across compact, midsize, and luxury market segments will be discussed.