# L-18 MCS 507 Mon 2 Oct 2023 : GUI model for 4-bar mechanism """ The GUI consists of one canvas to draw a 4-bar mechanism. A 4-bar mechanism consists of four rigid bars. The first bar, the crank, drives the mechanism. The first two scales at the left regulate the length of the crank and the angle of the crank. The horizontal scale below the canvas determine the position of the rightmost bottom joint, at the start of the right bar. The bar attached to the crank connects to the right bar. six scales and six corresponding labels. Five of the six scales determine the lenghts of the bars of the mechanims. """ from tkinter import Tk, Canvas, Entry, Label, Scale from tkinter import IntVar, DoubleVar, Button, Checkbutton from tkinter import W, E, LEFT, RIGHT, INSERT, END, ALL from fourbar import FourBar class FourBarGUI(object): """ GUI to model a 4-bar mechanism. """ def __init__(self, wdw, r, c): """ Determines layout of the canvas, number of rows and colums is r and c. """ wdw.title('a 4-bar mechanism') self.fbr = FourBar() self.rows = r self.cols = c self.ox = c/3 self.oy = 3*r/4 # print "A =" , (self.ox, self.oy) self.togo = False # the canvas and start, stop, and clear buttons self.c = Canvas(wdw, width=self.cols, height=self.rows, bg='green') self.c.grid(row=1, column=2, columnspan=2) self.startbut = Button(wdw, text='start', command = self.start) self.startbut.grid(row=3, column=2, sticky=W+E) self.stopbut = Button(wdw, text='stop', command = self.stop) self.stopbut.grid(row=3, column=3, sticky=W+E) self.clearbut = Button(wdw, text='clear', command = self.clear) self.clearbut.grid(row=3, column=4, columnspan=3, sticky=W+E) # the length of the crank self.crank_lbl = Label(wdw, text='crank', justify=LEFT) self.crank_lbl.grid(row=0, column=0) self.crank_bar = IntVar() self.L = Scale(wdw, orient='vertical', from_=0, to=self.rows/2, \ tickinterval=20, resolution=1, length=self.rows, \ variable=self.crank_bar, command=self.draw_mechanism) self.L.set(self.fbr.crank) self.L.grid(row=1, column=0) # the angle that drives the crank self.angle_lbl = Label(wdw, text='angle', justify=LEFT) self.angle_lbl.grid(row=0, column=1) self.angle = DoubleVar() self.t = Scale(wdw, orient='vertical', from_=0, to=6.30, \ tickinterval=0.30, resolution=0.01, length=self.rows, \ variable=self.angle, command=self.draw_mechanism) self.t.grid(row=1, column=1) self.angle.set(self.fbr.angle) # the bar at the right self.right_bar_lbl = Label(wdw, text='right bar', justify=LEFT) self.right_bar_lbl.grid(row=0, column=4) self.right_bar = IntVar() self.r = Scale(wdw, orient='vertical', from_=0, to=self.rows/2, \ tickinterval=20, resolution=1, length=self.rows, \ variable=self.right_bar, command=self.draw_mechanism) self.r.grid(row=1, column=4) self.right_bar.set(self.fbr.right) # the top bar attached to the crank self.top_bar_lbl = Label(wdw, text='top bar', justify=LEFT) self.top_bar_lbl.grid(row=0, column=5) self.r_top_bar = IntVar() self.R = Scale(wdw, orient='vertical', from_=0, to=self.rows/2, \ tickinterval=20, resolution=1, length=self.rows, \ variable=self.r_top_bar, command=self.draw_mechanism) self.R.grid(row=1, column=5) self.r_top_bar.set(self.fbr.top) # the scale for the coupler bar self.coupler_bar_lbl = Label(wdw, text='coupler', justify=LEFT) self.coupler_bar_lbl.grid(row=0, column=6) self.coupler_bar = IntVar() self.cpl = Scale(wdw, orient='vertical', from_=0, to=self.rows/2, \ tickinterval=20, resolution=1, length=self.rows, \ variable=self.coupler_bar, command=self.draw_mechanism) self.cpl.grid(row=1, column=6) self.coupler_bar.set(self.fbr.coupler) # the horizontal bottom bar self.flat_lbl = Label(wdw, text='right joint', justify=RIGHT) self.flat_lbl.grid(row=2, column=1) self.flat = IntVar() self.f = Scale(wdw, orient='horizontal', from_=0, to=self.rows/2, \ tickinterval=50, resolution=1, length=self.cols, \ variable=self.flat, command=self.draw_mechanism) self.f.grid(row=2, column=2, columnspan=2) self.flat.set(self.fbr.flat) # coordinates of the coupler point appear on top self.ex = Entry(wdw) # for x value self.ex.grid(row=0, column=2) self.ex.insert(INSERT, "x = ") self.ey = Entry(wdw) # for y value self.ey.grid(row=0, column=3) self.ey.insert(INSERT,"y = ") # check button for drawing of coupler curve self.curve = IntVar() self.cb = Checkbutton(wdw, text='coupler', \ variable=self.curve, onvalue=1, offvalue=0) self.curve.set(1) self.cb.grid(row=3, column=0) # draw the mechanism on canvas self.draw_mechanism(0) def update_values(self): """ Takes all values of the scales and updates the data attributes of self.fbr. """ self.fbr.flat = self.flat.get() self.fbr.crank = self.crank_bar.get() self.fbr.top = self.r_top_bar.get() self.fbr.right = self.right_bar.get() self.fbr.coupler = self.coupler_bar.get() self.fbr.angle = self.angle.get() #self.fbr.print_joints() def draw_coupler_point(self, p): """ Draws coupler point with coordinates in p if the curve checkbox is on. Note that the previous values for the coordinates of the coupler point are stored in the entry fields. """ if self.curve.get() == 1: px = self.ox + p[0] py = self.oy - p[1] eqx = self.ex.get() Lx = eqx.split('=') if Lx[1] == ' ': qx = 0.0 else: qx = float(Lx[1]) eqy = self.ey.get() Ly = eqy.split('=') if Ly[1] == ' ': qy = 0.0 else: qy = float(Ly[1]) if (qx != 0.0) and (qy != 0.0): qx = self.ox + qx qy = self.oy - qy self.c.create_line(qx, qy, px, py, width=1) def fill_entries(self, p): """ Fills the entry fields with the coordinates of the coupler point in p. """ sx = 'x = %f' % p[0] sy = 'y = %f' % p[1] self.ex.delete(0, END) self.ex.insert(INSERT, sx) self.ey.delete(0, END) self.ey.insert(INSERT, sy) def draw_link(self, p, q, s): """ Draws the link from point with coordinates in p to the point with coordinates in q, using s as tag. """ self.c.delete(s) px = self.ox + p[0] py = self.oy - p[1] qx = self.ox + q[0] qy = self.oy - q[1] self.c.create_line(px, py, qx, qy, width=2, tags=s) def draw_mechanism(self, v): """ Fills the canvas with the current model of the planar 4-bar mechanism. Because this command is called by the sliders, the argument v is needed but not used. """ self.update_values() L = self.fbr.joints() for i in range(0, len(L)): p = L[i] px = self.ox + p[0] py = self.oy - p[1] sj = 'joint%d' % i self.c.delete(sj) self.c.create_oval(px-6, py-6, px+6, py+6, width=1, \ outline='black', fill='red', tags=sj) self.draw_link(L[0], L[2], 'link0') self.draw_link(L[1], L[3], 'link1') self.draw_link(L[2], L[3], 'link2') self.draw_link(L[2], L[4], 'link3') self.draw_coupler_point(L[4]) self.fill_entries(L[4]) def start(self): """ Starts the animation, adding 0.01 to angle. """ self.togo = True while self.togo: theta = self.angle.get() theta = theta + 0.01 if theta > 6.28: theta = 0 self.angle.set(theta) self.draw_mechanism(0) self.c.update() def stop(self): """ Stops the animation. """ self.togo = False def clear(self): """ Clears the canvas. """ self.c.delete(ALL) def main(): """ Sets the dimensions and launches the GUI. """ top = Tk() r = 400 c = 600 FourBarGUI(top, r, c) top.mainloop() if __name__ == "__main__": main()