A Basic Product Application: Redesign of a Toy Solar Car

http://www.youtube.com/watch?v=V7egS3u2z4U

Let's apply this factorial design approach to a product design. Inthis case, the product is a toy solar car, sold in hobby and toy stores. We wish to evolve the product to improve its performance for the customers. The product design statement is "develop an evolved a toy solar car product that is competitive, robust, and satisfies the customer needs" (Figure 18.14). Using this problem statement, possible improvements of the solar car, from customer need analysis and product teardown, include solar panel/collection areas, power efficiency, manufacturing cost and assemblability, aesthetics (model an actual race car instead of a pinewood derby car), speed, and maneuverability. For the purposes of this example, increasing car speed is our focus.

Let's now consider a clarification of the product development to understand what parameters affect car speed. A high-level physical principle of the car speed may be stated as:

where wis the angular velocity of the motor output (rpm), r_g is the radius of the pinion (motor) gear, r_rw is the radius of the rear wheel, and r_rg is the radius of the rear internal gear. Likewise, general physical principles for the motor speed and torque are given by:

where T is the motor torque, is the coefficient of friction in the rear axle, is the coefficient of friction in the front axle, W_r is the weight non the rear axle, W_f is the weight on the front axle, and P is the available motor power. These variables should be considered as possible factors in our physical model.

Let's consider when the motor speed and torque relationships (functions f and g) are not readily available. For this situation, the motor may also be modeled with a dc torque speed relationship, estimated by

This linear relationship of torque-speed for a dc motor may be determined a variety of ways. For example, if we consider the average speed of the current solar car, v = D/t, where D = distance traveled and t = time, we can determine the torque speed curve of the motor by placing different weights on the car, measuring the time to travel a given distance (holding solar power constant), and backing out torque through the wheels and drive train of the car.

These qualitative models provide us with a number of insights into the engineering problem at hand, that is, development of an empirical model for improving the speed of the solar car (our customer need focus). Let's now apply the experimental design procedure for developing an empirical model.

http://www.youtube.com/watch?v=40dOyZIVlPw

Date: 2016-01-14; view: 618