1 00:00:00,060 --> 00:00:05,040 From this section, we'll start to investigate force control in robotic manipulators. 2 00:00:05,640 --> 00:00:08,520 We have learned position control schemes until now. 3 00:00:08,850 --> 00:00:13,620 But force control is at least as important as position control also. 4 00:00:14,310 --> 00:00:17,820 There are different kind of task tasks in robotic manipulation. 5 00:00:18,330 --> 00:00:22,410 These tasks can be without interruption and without interruption. 6 00:00:22,410 --> 00:00:30,660 Interaction tasks that do not contain interaction can be pick and place wielding, painting, controlling 7 00:00:30,660 --> 00:00:33,870 orientation of an object such as camera and so on. 8 00:00:34,290 --> 00:00:40,020 In these kind of applications, we can use pure position and orientation control schemes. 9 00:00:40,650 --> 00:00:46,650 However, the tasks that contain interactions such as assembly, polishing, cleaning, cutting and 10 00:00:46,650 --> 00:00:50,370 so on requires control of interaction forces. 11 00:00:50,730 --> 00:00:58,200 So we need in these kind of applications either pure force control or generally hybrid control, namely 12 00:00:58,200 --> 00:01:03,150 both position and force control, as we have said. 13 00:01:03,300 --> 00:01:08,520 These kind of tasks require our control interaction forces or contact forces. 14 00:01:09,630 --> 00:01:15,900 Now you can ask why we need to have separate control mechanisms to control interaction forces, why 15 00:01:15,900 --> 00:01:21,090 we can't apply position controllers to control forces, also to control forces also. 16 00:01:21,520 --> 00:01:24,480 Let's investigate this issue a little bit. 17 00:01:25,410 --> 00:01:32,030 Let's assume that we have given task of inserting some object in the hall as a control mechanism. 18 00:01:32,040 --> 00:01:34,130 We use simple idea control. 19 00:01:34,680 --> 00:01:40,890 Let's say that a robot model and environment models have some inaccuracies, which is quite normal in 20 00:01:40,890 --> 00:01:45,390 practical applications because we cannot model everything precisely. 21 00:01:45,720 --> 00:01:48,380 So then inserting object into the whole. 22 00:01:48,390 --> 00:01:53,640 There are small misalignment and objects stuck near Holt and defectors. 23 00:01:53,640 --> 00:01:58,950 Current position is X and the desired position is indicated as X. 24 00:01:59,360 --> 00:02:03,090 The error is difference of these to these two quantities. 25 00:02:03,570 --> 00:02:11,100 As error is non-zero, proportional control tries to increase input force in order to decrease the error. 26 00:02:11,460 --> 00:02:18,180 But both environment and the robot is stiff, so huge interaction forces arise between robot and the 27 00:02:18,180 --> 00:02:19,020 environment. 28 00:02:19,590 --> 00:02:25,740 This can cause either breaking down of object or robot, which are not desired at all. 29 00:02:26,250 --> 00:02:32,610 As you can see, not taking into consideration interaction forces and applying purely position control 30 00:02:32,620 --> 00:02:35,390 blindly can cause huge problems. 31 00:02:35,400 --> 00:02:41,100 In order to avoid these kind of issues, either the robot or the environment has to be made compliant, 32 00:02:41,910 --> 00:02:43,860 so stiffness has to be controlled. 33 00:02:44,190 --> 00:02:48,480 Additionally, contact control contact forces also have to be controlled. 34 00:02:49,140 --> 00:02:53,700 OK, we now have a bit of idea about force control and its importance. 35 00:02:54,060 --> 00:03:00,300 Force control can be indirect, in which case it is achieved through motion control without using force 36 00:03:00,300 --> 00:03:01,200 torque sensors. 37 00:03:01,530 --> 00:03:07,770 So without force feedback, loop stiffness, compliance control, impedance control belongs to this 38 00:03:07,770 --> 00:03:08,340 category. 39 00:03:08,670 --> 00:03:14,370 However, this kind of control requires proper model of the environment, which is not always easy to 40 00:03:14,370 --> 00:03:15,000 obtain. 41 00:03:15,620 --> 00:03:22,020 Interrupt Force Control Force is controlled up to desired value by utilizing force torque sensors. 42 00:03:22,290 --> 00:03:30,410 So through force feedback, loop force control, hybrid force, motion control belong to this category. 43 00:03:30,450 --> 00:03:35,340 This kind of control requires force torque sensors, which are quite expensive. 44 00:03:35,910 --> 00:03:38,580 That's all about introduction to force control.