Class for controlling and plotting n-link arm

Author: daniel-s-ingram

RoboticArm/NLinkArm.py

@@ -0,0 +1,62 @@
+"""
+Class for controlling and plotting an arm with an arbitrary number of links.
+
+Author: Daniel Ingram
+"""
+
+import numpy as np
+import matplotlib.pyplot as plt
+
+class NLinkArm(object):
+    def __init__(self, link_lengths, joint_angles, goal):
+        self.n_links = len(link_lengths)
+        if self.n_links is not len(joint_angles):
+            raise ValueError()
+
+        self.link_lengths = np.array(link_lengths)
+        self.joint_angles = np.array(joint_angles)
+        self.points = [[0, 0] for _ in range(self.n_links+1)]
+
+        self.lim = sum(link_lengths)
+        self.goal = np.array(goal).T
+
+        self.fig = plt.figure()
+        self.fig.canvas.mpl_connect('button_press_event', self.click)
+
+        plt.ion()
+        plt.show()
+
+        self.update_points()
+
+    def update_joints(self, joint_angles):
+        self.joint_angles = joint_angles
+        self.update_points()
+
+    def update_points(self):
+        for i in range(1, self.n_links+1):
+            self.points[i][0] = self.points[i-1][0] + self.link_lengths[i-1]*np.cos(np.sum(self.joint_angles[:i]))
+            self.points[i][1] = self.points[i-1][1] + self.link_lengths[i-1]*np.sin(np.sum(self.joint_angles[:i]))
+
+        self.end_effector = np.array(self.points[self.n_links]).T
+        self.plot()
+
+    def plot(self):
+        plt.cla()
+
+        for i in range(self.n_links+1):
+            if i is not self.n_links:
+                plt.plot([self.points[i][0], self.points[i+1][0]], [self.points[i][1], self.points[i+1][1]], 'r-')
+            plt.plot(self.points[i][0], self.points[i][1], 'ko')
+
+        plt.plot(self.goal[0], self.goal[1], 'gx')
+
+        plt.plot([self.end_effector[0], self.goal[0]], [self.end_effector[1], self.goal[1]], 'g--')
+
+        plt.xlim([-self.lim, self.lim])
+        plt.ylim([-self.lim, self.lim])
+        plt.draw()
+        plt.pause(0.0001)
+
+    def click(self, event):
+        self.goal = np.array([event.xdata, event.ydata]).T
+        self.plot()