Schematic diagram of VC-based courseware simulation of involute gear-gear transmission based on VCFig.1 is a static diagram of a certain moment of interception of CAI courseware for simulating involute gear meshing transmission based on VC. Two places can be seen from the figure. The meshing points (A, B) can be judged that the meshing point is always on a fixed straight line. This fixed straight line is actually the meshing trajectory, and the linear motion of the meshing point in the fixed direction during the simulation is very clear.
Figure 2 shows the involute curve. The involute curve occurs. When the straight line NK is purely rolled along the fixed circle O, the trajectory of any point K on the line is called the involute of the circle. . It can be seen that the involute curve is a continuous curve, and any point on the curve is conductive. That is to say, the coordinate values ​​of all points on the curve are floating point continuous, and the number of points is uncountable. However, the coordinate values ​​of the points displayed on the computer screen are non-continuous, and are orthogonally distributed. The number of displayed points is limited. For example, the resolution is 1024*768, and the screen image point is 786432 points, so only limited points can be used instead of infinity. Point, replace the exact point on the curve with the approximate point. In the direction of the height of the gear teeth, we find a number of points on the contour line, and then connect these points in a straight line segment. This set of line segments forms the approximate contour of the tooth profile. This method is called straight line fitting method. The more points or straight line segments are fitted, the higher the accuracy of the tooth profile; in addition, the arc fitting method has higher contour accuracy, but the program and calculation are more complicated. When calculating the fitting point, it should be noted that when the gear base circle is larger than the root circle, the tooth profile will be cut off from the root to the base circle, which can be approximated by a straight line segment, and the involute formula is used outside the base circle. Calculation.
The K-point coordinate formula is: X=rk*SIN(θk), Y=rk*COS(θk), (assuming the starting angle of the first involute is on the Y-axis; where Rk is the base circle and the root circle The larger of them, θk=tan(Ak)-Ak, Ak=ARCCOS(rb/rk), rk=Rk+dh, rk is any point on the involute, dh is to divide the tooth height into one part. The smaller the dh value, the higher the fitting accuracy). The programming statement that draws the involute is the for statement in VC++, which performs multi-point calculation and multi-line drawing. Draw an involute subroutine as large as the following (because there are more program statements, only the basic idea is given here for reference): Start drawing the involute function name (that is, the subroutine entry address) to calculate the starting point of the involute. Move the pen to this point (at 1 o'clock in the figure) For statement (the rk value increases dh every time, and judges whether it has reached the top of the tooth (at 2 o'clock in the figure), the following work is done below the tooth top) One fits the point coordinates, and draws all the involutes and the animation forming principle to draw all the involutes from the straight line to the end of the point (the subroutine exit address). Just determine the distribution angle of the other involutes and modify the coordinate formula. It is: X=rk*SIN((i*360/z)+θk), Y=rk*COS((i*360/z)+θk), where i is the serial number of a tooth and z is the number of teeth of the gear. The animation mainly completes the rotation of the gear, and the animation is formed by re-drawing all the involutes at regular intervals T in the circumferential direction, and the starting angle MJ of each involute is offset each time the redraw is repeated. A fixed value, which is 1 degree each time in our program, visually forms the animation of the gear rotation. By changing the time T, the gear rotation speed can be changed. At this time, the coordinate value of the K point is finally expressed as: X = rk * SIN ((i * 360 / z) + θk + MJ), Y = rk * COS ((i * 360 / z) + θk + MJ).
Introduction to Programming The CAI software was developed on the XP operating system platform using the visual object programming software VC++6.0. The interface is friendly and easy to operate. The main functions are: change parameters, animation demonstration (including continuous presentation, single step presentation, pause), error prompt, exit function. The CAI software can also be compiled with VB, programmed with VB, easy to learn and easy to get on the road, suitable for beginner programmers. In the preparation of the simulation program, in the vivid, visual, intuitive, realistic, easy to operate principle, drawing the involute and animation display as the core, the display effect should be changed immediately due to the change of parameters.
Most of the modern programming methods are based on visual object programming, driven by WINDOWS messages, and there is a great difference between the program and the structure control structure. It can be said that the programming and methods have a qualitative leap. It is difficult to control the process and upgrade the program. Functional realization, modular design, and program upgrade are easy. The following are the main functional modules of the CAI software program (also called classes in VC++ programming) for reference.
Module one: gear parameter modification and calculation module, dynamic notification module two, module three.
Module 2: Static involute draw function module, and call for module three, the code can be reused in other applications.
Module 3: The animation drawing module continuously calls the module 2 to generate animation effects, and the modification code is convenient.
Module 4: Exception Handling and Error Prompt Module.
The simulation program has been successfully run on the XP operating system and the effect is good. Received the praise of students and teachers. In front of the computer, the students simulate the meshing process again and again, from time to time to modify the gear parameters and change the animation display effect, for a long time refused to leave. Many students have repeatedly pondered how the program was compiled, how the animation was implemented, and asked what programming techniques and related knowledge the teacher used. The program is difficult, long, and so on. The students realized that they must not only learn the major, but also learn the computer to solve the practical problems better and more scientifically. At present, we are further improving this CAI software, such as improving the drawing precision of the involute and the smoothness of the outline of the image, enhancing the animation display effect, improving the human-machine interface, expanding the new functions, and letting this CAI software be taught in the future. Play a bigger role.
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