1 00:00:00,060 --> 00:00:00,480 OK. 2 00:00:00,780 --> 00:00:06,990 In the previous lesson, we have seen general information about force control in this lesson, we will 3 00:00:06,990 --> 00:00:14,430 see RCC or Remote Center of Compliance, which is used in robotics to provide artificial compliance 4 00:00:14,550 --> 00:00:20,940 to the robot arm on premise less than we have seen the importance of compliance in robotic applications. 5 00:00:21,450 --> 00:00:27,510 The issue is that generally the robots and environment are stiff, especially the environment can be 6 00:00:27,510 --> 00:00:28,110 very stiff. 7 00:00:28,410 --> 00:00:33,900 So we have to control the stiffness in order to control interaction forces, by some way. 8 00:00:34,470 --> 00:00:40,140 We can provide compliance in two ways, namely passive compliance and active compliance. 9 00:00:40,530 --> 00:00:43,890 Passive compliance is generated through mechanical devices. 10 00:00:44,370 --> 00:00:49,380 RCC or remote sensing of compliance is one of these mechanical devices. 11 00:00:49,770 --> 00:00:55,800 The advantage of this method of providing compliance is that it doesn't require sophisticated control 12 00:00:55,800 --> 00:00:57,330 algorithms or sensors. 13 00:00:57,930 --> 00:01:01,380 You will have to just connect it to your robot manipulator. 14 00:01:01,680 --> 00:01:04,530 But the problem is that the robots are not standard. 15 00:01:04,950 --> 00:01:07,170 Also, robotic tasks are not standard. 16 00:01:07,470 --> 00:01:11,610 So depending on task and robot, this device has to be changed. 17 00:01:12,060 --> 00:01:15,150 This means additional cost and low flexibility. 18 00:01:16,620 --> 00:01:23,370 Active compliance in opposite provide compliance through control algorithms so you can provide specific 19 00:01:23,370 --> 00:01:26,580 level of stiffness or compliance by algorithm. 20 00:01:27,000 --> 00:01:30,450 You may need for stored sensors to achieve this level of control. 21 00:01:30,870 --> 00:01:36,990 By this method, you will get high operational flexibility because there is no robot or task dependent 22 00:01:36,990 --> 00:01:42,840 device, but you will need sophisticated algorithms, which includes computational complexity. 23 00:01:43,440 --> 00:01:48,360 Additionally, you may need the model of environment, which can be difficult to obtain. 24 00:01:49,110 --> 00:01:51,420 So what is the center of compliance? 25 00:01:51,870 --> 00:01:57,080 Let's assume below situation the apply force being in blue. 26 00:01:57,090 --> 00:02:00,630 We apply purely horizontal force in red. 27 00:02:00,660 --> 00:02:02,280 We apply pure torque. 28 00:02:02,850 --> 00:02:10,020 However, as you can see from second stage, even we apply pure the horizontal force on pure torque. 29 00:02:10,230 --> 00:02:16,560 We get combination of rotational and translational motions, so transnational motion and rotational 30 00:02:16,560 --> 00:02:17,730 motion are coupled. 31 00:02:18,150 --> 00:02:22,260 You want to decouple them because of the reasons you will see in the minute. 32 00:02:22,920 --> 00:02:30,600 In the third stage, you see that we get only translational motion due to horizontal force and rotational 33 00:02:30,600 --> 00:02:32,250 motion due to pure torque. 34 00:02:32,700 --> 00:02:40,210 This point is called centre of compliance, so centre of compliance is the point in which translation 35 00:02:40,210 --> 00:02:42,990 and motion and rotational motion are decoupled. 36 00:02:43,230 --> 00:02:45,480 So what is a remote centre of compliance? 37 00:02:46,080 --> 00:02:52,890 As we have said before, it's a mechanical device to provide passive compliance, as you can see from 38 00:02:52,890 --> 00:02:53,530 the picture. 39 00:02:53,550 --> 00:02:57,480 It consists of springs that provides six degrees of freedom. 40 00:02:57,990 --> 00:03:02,640 In this picture, you can see the functionality of our CC upper. 41 00:03:02,640 --> 00:03:08,850 Part of our CC is connected to the rest of the robot arm, and this is the gripper of the robot arm. 42 00:03:09,330 --> 00:03:12,570 RCC provides centre of compliance in that point. 43 00:03:12,990 --> 00:03:16,920 As you can see, it is not inside of CC, but outside. 44 00:03:17,280 --> 00:03:21,330 So that's why this device is called a remote symbol of compliance. 45 00:03:21,780 --> 00:03:29,310 It's obvious from picture that we have lateral and cooking's alignment during assembly if we don't provide 46 00:03:29,310 --> 00:03:31,140 compliance to the robot arm. 47 00:03:31,380 --> 00:03:37,320 These misalignments can cause serious issues, however, due to the centre of compliance created by 48 00:03:37,330 --> 00:03:45,270 our CC, single point control forces create translational motion only, while two point contact forces 49 00:03:45,270 --> 00:03:46,830 create rotational motion. 50 00:03:47,430 --> 00:03:51,060 So, by this way, misalignments have been compensated for. 51 00:03:52,110 --> 00:03:56,580 In this video, you can see RTC in action. 52 00:04:07,170 --> 00:04:14,310 From the video, it is obvious how misalignments are compensated for due to the provided compliance. 53 00:04:14,610 --> 00:04:21,420 So all in all, RCC, which provides passive compliance, is a simple and moderately cheap solution. 54 00:04:22,050 --> 00:04:26,190 However, it is not very flexible and application dependent. 55 00:04:26,640 --> 00:04:32,520 Based on some parameter requirements change, and for this reason, RCC has to be changed. 56 00:04:32,530 --> 00:04:40,860 Also, in the next few lessons, we will see other methods that are better than RCC in terms of flexibility 57 00:04:41,100 --> 00:04:42,900 and providing compliance.