diff --git a/01_introduction-motivation-and-background/QuizWeek1 b/01_introduction-motivation-and-background/Quiz - WEEK 1 similarity index 81% rename from 01_introduction-motivation-and-background/QuizWeek1 rename to 01_introduction-motivation-and-background/Quiz - WEEK 1 index 2910aa8..3b4563a 100644 --- a/01_introduction-motivation-and-background/QuizWeek1 +++ b/01_introduction-motivation-and-background/Quiz - WEEK 1 @@ -1,5 +1,6 @@ +CSDN版本：https://blog.csdn.net/qq_39537898/article/details/104184033 /*********************************************************/ -/*** QUIZ 1.1.1 Why and how do animals move ***/ +/*** QUIZ 1.1.1 Why and how do animals move ***/ **********************************************************/ 1. In Newton's F=m·a, what does F denote? - Force @@ -9,6 +10,22 @@ - Tail turns to the left 4. Which is an example of intelligence "baked into" the body? - The kangaroos legs acting as springs + +/*********************************************************/ +/*** QUIZ 1.1.2 Bioinspiration ***/ +**********************************************************/ + 1.The speed of airplanes is often described in units of Mach (the speed of sound at standard sea level conditions). What is the speed of Helios 2 in Mach? + 207 + + 2.Acceleration is sometimes measured in g (acceleration due to gravity at the Earth’s surface). What is the cheetah’s acceleration in units of g? + 1.3 + 解释：记得看清这里的单位是，几个g的加速度 + + 3.Turning left “at the house with the red roof” is an example of navigation using which part of the hippocampus? + Place cells + + 4.Turning left “after 25 meters” is an example of navigation using which part of the hippocampus? + Grid cells /*********************************************************/ /*** QUIZ 1.1.3 Legged Mobility: dynamic motion and the***/ @@ -17,26 +34,26 @@ 1. In the above image, we see three robots with the leg forces on the ground drawn in blue. Match the robots with their resulting jumps. a) Robot "a" will jump the highest up, robot "b" will jump the furthest sideways. b) Robot "c" will jump the highest up, robot "b" will jump the furthest sideways. - c) Robot "b" will jump the highest up, robot "a" will jump the furthest sideways. CORRECT + ✔c) Robot "b" will jump the highest up, robot "a" will jump the furthest sideways. CORRECT d) Robot "a" will jump the highest up, robot "a" will jump the furthest sideways. 2. Hamiltonian systems have their total energy (sum of potential and kinetic energies) conserved. Which of these can best be modeled as a Hamiltonian system. a) A block sliding down a ramp covered in honey b) A car decelerating at a red light c) An air conditioner unit - d) A pendulum in a clock swinging back and forth CORRECT + ✔d) A pendulum in a clock swinging back and forth CORRECT 3. Assuming these two motors are about the same size, which one will likely produce more torque and which one will have higher inertia? - a) The motor on the right will produce more torque and have higher inertia. CORRECT + ✔a) The motor on the right will produce more torque and have higher inertia. CORRECT b) The motor on the left will produce more torque and have higher inertia. c) The motor on the right will produce more torque, the motor on the left will have higher inertia. d) The motor on the left will produce more torque, the motor on the right will have higher inertia. e) Both motors will produce the same torque and have the same inertia. 4. Which are examples of programming work? No son todas, ni la cuarta sola. - a) A robot running over rough terrain + ✔a) A robot running over rough terrain CORRECT b) A robot using a sensor to scan the environment - c) A robot opening a door + ✔c) A robot opening a door CORRECT d) A robot making a decision about which way to go /*********************************************************/ @@ -74,4 +91,4 @@ It turns out that the nonlinear solutions also oscillate but we need more advanced methods to show this mathematically. 2. Linearize the equations of motion of an undamped pendulum with equation of motion second derivate θ=−g·sin(⁡θ)/l about the point θ=π, derivate θ=0. Sol: -g/l - You should get a Jacobian [0 1; g/l 0]. This matrix has one positive and one negative eigenvalue. Since the linearized dynamics are hyperbolic we can predict the nonlinear stability behavior from that of the linearized dynamics (which our eigenvalue analysis indeed shows to be unstable). \ No newline at end of file + You should get a Jacobian [0 1; g/l 0]. This matrix has one positive and one negative eigenvalue. Since the linearized dynamics are hyperbolic we can predict the nonlinear stability behavior from that of the linearized dynamics (which our eigenvalue analysis indeed shows to be unstable). diff --git a/02_behavioral-templates-physical-bodies/QuizWeek2 b/02_behavioral-templates-physical-bodies/Quiz - WEEK 2 similarity index 89% rename from 02_behavioral-templates-physical-bodies/QuizWeek2 rename to 02_behavioral-templates-physical-bodies/Quiz - WEEK 2 index 6d90124..2a612da 100644 --- a/02_behavioral-templates-physical-bodies/QuizWeek2 +++ b/02_behavioral-templates-physical-bodies/Quiz - WEEK 2 @@ -1,3 +1,4 @@ +CSDN版本:https://blog.csdn.net/qq_39537898/article/details/104184033 /*********************************************************/ /*** QUIZ 2.1.1 Walking like a rimless wheel ***/ **********************************************************/ @@ -5,51 +6,53 @@ a) COT = Sin(rampAngle) b) COT = Cos(rampAngle) - c) COT = Tan(rampAngle) -> This one + ✔c) COT = Tan(rampAngle) -> CORRECT d) COT = Csc(rampAngle) e) COT = Sec(rampAngle) f) COT = Cot(rampAngle) 2. The Cornell Ranger has a mass of 9.91 kg and walked a total distance of 65,243 m using 1,774,800 J of battery energy. What is the cost of transport for the Cornell Ranger? Assume a gravitational acceleration of 9.81 m/s^2 in calculating your answer. - + + ✔0.28 + COT = E / mgd; E = Energy input of the system, m = mass, d = distance, g = standard gravity. COT = 1774800/(9.91*9.81*65243) = 0.27981 3. What ramp angle is required to give a cost of transport of 0.2 for the rimless wheel, which is approximately equal to the efficiency of human walking? - a) 6 degrees -> No es correcta - b) 11 degrees + a) 6 degrees + ✔b) 11 degrees -> CORRECT c) 31 degrees d) 45 degrees - + 解释：arctan(0.2)=11 + 4. We've seen that energy is often used very efficiently for movement in biology as compared to in robots. The cost of storing energy (in terms of weight) is another factor that comes into play in determining locomotion ability -- the more weight is stored in fuel, the more mass the actuators need to move! Let's compare how much it weights to store a given amount of energy in biological fuel -- i.e. food -- as compared with electricity to power a robot. - How many kg of battery weight would it be necessary for a human-like robot to walk a marathon? Assume that a marathon takes 5960 KJ to walk (this is an extremely roughly estimate assuming a 72 kg person walking it with a energetic cost of transport of 0.2), and that the lithium polymer batteries have a mass of 0.002kg per KJ of energy storage. Round to the nearest kilogram. - Just to put this in perspective, this same energy can be contained in less than 7 candy bars, which have a total weight of less than 0.4kg! - + + ✔12 Energy required for marathon * KJ per battery = 5960KJ * 0.002 KJ per battery = 11.92 -> 12KG. /*********************************************************/ -/*** QUIZ 2.1.2 ***/ +/*** QUIZ 2.1.2 Running like a spring-loaded pendulum ***/ ***/ **********************************************************/ 1. Given a robot with a leg length of 0.4m, what is the estimated maximum possible walking speed in meters per second according to the Froude number? Assume an acceleration due to gravity of 10m/s^2. - + + ✔2 Fr = v² / g·l -> v = sqrt(Fr·g·l), donde Fr < 1 para correr y Fr > 1 para caminar - Por tanto, v = 2 2. Assume that the energetically optimal walk-to-run transition speed for a robotic biped occurs at a Froude number of 0.5. What is the expression for the optimal speed of transitioning from walking to running in terms of leg length d? Assume a gravitational acceleration of 10m/s^2. Enter you answer in simplest form, using sqrt() to represent any square roots. (Ex: The square root of 2*d is written as sqrt(2*d)). - v = sqrt(5·d) - - 3. Which of the following energy plots best represents the energy during stance of the center-of-mass of a robot running with SLIP-like dynamics? The blue curve shows kinetic energy and the red curve shows gravitational potential energy. Assume the horizontal axis is time and the vertical axis is energy. - - La 4. Las dos curvas son idénticas. Se puede observar en: Evidence for Spring Loaded Inverted Pendulum Running in a Hexapod Robot, página 7. + ✔v = sqrt(5·d) + 3. Which of the following energy plots best represents the energy during stance of the center-of-mass of a robot running with SLIP-like dynamics? The blue curve shows kinetic energy and the red curve shows gravitational potential energy. Assume the horizontal axis is time and the vertical axis is energy. + + ✔两个下凸的图 + 4. Here is actual data for the center-of-mass trajectory of a robot running primarily in the directions labeled y and z. From this data, which template best explains the motion observed? - a) Lateral leg spring (LLS) -> Correcta + ✔a) Lateral leg spring (LLS) -> CORRECT b) Ackermann vehicle c) Rimless wheel @@ -67,18 +70,20 @@ Your first task is to tune the thrust duration using the slider so that the hopper reaches a steady state hopping height between 1m and 1.1m (denoted by the horizontal green and red lines in the generated plot) at the end of the simulation. Give the resulting thrust duration in seconds that meets these goals as your answer. - P = 0.00065 + ✔0.00071429 2. Now we will tune the forward speed controller. You run the simulation by running Quiz_2_1_1_Question_2 with no arguments. Recall that the neutral point is estimated at each step, and that the forward speed controller consists of a proportional controller that puts the toe in front of or behind the neutral point to obtain the desired speed. What proportional gain to the forward speed controller causes the robot to accelerate from rest to a speed between 0.9 m/s and 1.1 m/s without ever going over 1.1 m/s? - P = 0.1 + ✔0.087439 3. Now we will tune the pitch controller to achieve a desired pitch of π12 radians. You run the simulation by running Quiz_2_1_1_Question_3 with no arguments. Your task is to finish writing the PD controller contained in pitchController.m. Keep a derivative term of kd_phi = 5. What value of kp_phi bounds the pitch within the green and red lines in the graph generated by the simulation? - + + ✔5 + En el script pitchController.m function Tphi = pitchController(phi,phiDesired,dphi_dt) @@ -103,7 +108,7 @@ b) Perimeter: 2x Area: 2x Volume: 2x - c) Perimeter: 2x -> Correcta + ✔c) Perimeter: 2x -> CORRECT Area: 4x Volume: 8x d) Perimeter: 2x @@ -123,10 +128,11 @@ Hint: stress is mass divided by area. Assuming constant density of the animals, mass is proportional to volume. Also assume that the volume scales with length^3. Remember that the primary compression occurs axially along the length of the bone. How much larger must the thickness be to maintain the same (mass)/(cross sectional area) ratio? Correct answers should be submitted with one decimal place, (e.g, 23.5) + + ✔0.11 - El volumen aumenta por 3 veces también. - - V = 3*3*3 = 27 -> sqrt(V) = 5.19 ~ 5.2 + El volumen aumenta por 3 veces también. + V = 3*3*3 = 27 -> sqrt(V) = 5.19 ~ 5.2 4. Pair the following scenarios with the dominant mode of loading: 1) a rubber band being stretched @@ -138,7 +144,7 @@ 2) compression 3) bending 4) tension - b) 1) tension -> Correcta + ✔b) 1) tension -> CORRECT 2) bending 3) compression 4) torsion @@ -160,24 +166,28 @@ **********************************************************/ 1. With everything else being equal (stiffness, strength, dimensions, etc.) which type of material will heat up more if stressed in tension until failure? - a) Ductile -> Correct + ✔a) Ductile -> CORRECT b) Brittle 2. If a 10cm diameter, 0.5m long cylinder is loaded with 20kg mass in tension, what is the stress (force divided by cross-sectional area) in the material in Pascals (the SI unit for stress: N/m^2)? (Remember, we are concerned with axial tension loads) - + + ✔24972.4 + stress = F/A; F = m*g = 20kg*9.8m/s² = 196.133 N; A = pi*r² = pi*0.05m² = 0.00785m²; - F = 196.133N / 0.00785m² = 24972.4N/m²; -> Correcta + F = 196.133N / 0.00785m² = 24972.4N/m²; -> CORRECT 3. If the above cylinder then stretches by 8cm, what is the strain (extension normalized by initial length) in %? - - strain = ðL / L = 0.08 / 0.5 = 0.16 = 16% -> Correcta + + ✔16 + + strain = ðL / L = 0.08 / 0.5 = 0.16 = 16% -> CORRECT 4. Necking is a phenomena where plastic deformation induces significant strain resulting in decreased cross sectional area. If the above cylinder experiences "necking" will the stress in the neck be larger or smaller than the stress in the rest of the sample? a) Smaller - b) Larger -> Correcta, porque el estrés depende inversamente del área de la sección. + ✔b) Larger -> CORRECT /*********************************************************/ /*** QUIZ 2.2.3 Design: figures of merit, robustness ***/ @@ -189,37 +199,45 @@ If a "spring" were to be made by pulling a 10cm long cylinder of material in tension with a desired stiffness of 5000kN/m, what should the diameter (in millimeters) be for an Aluminum "spring"? This wikipedia page (https://en.wikipedia.org/wiki/Young%27s_modulus) may be helpful, specifically the section : "Force exerted by stretched or contracted material". - - F = (EA/L0)*ðL -> F*L0 = E * pi * r² -> r = sqrt(F*L0/(E*pi)); - r[m] = sqrt(5000*0.1/(69*pi)) = 1.51[m] - r[mm] = 1518.7[mm] - ---- - d = sqrt((4*K*L)/(E*pi)); - Ø = 3.037494611[mm] + + ✔3.04 -> CORRECT + + F = (EA/L0)*ðL -> F*L0 = E * pi * r² -> r = sqrt(F*L0/(E*pi)); + r[m] = sqrt(5000*0.1/(69*pi)) = 1.51[m] + r[mm] = 1518.7[mm] + ---- + d = sqrt((4*K*L)/(E*pi)); + Ø = 3.037494611[mm] 2. If the "spring" were to be made of ABS plastic instead, what should the diameter be (in millimeters)? - - Ø = 17.010955993 [mm] + + ✔17.01 -> CORRECT + Ø = 17.010955993 [mm] 3. What would be the mass of the aluminum "spring" (in grams)? - + + ✔1.96 -> CORRECT + + 解释：质量=密度*体积 La masa de un cilindro es: densidad = masa/volumen -> masa = densidad * volumen. volumen = pi * r² * L; masa[g] = 2.7 g/cm^3 * pi * (0.304/2)² [cm²] * 10 [cm] = 0.623808[g] 4. What would be the mass of the plastic "spring" (in grams)? - + + ✔3.197 -> CORRECT + masa[g] = 1.3 g/cm^3 * pi * (1.701/2)² [cm²] * 10 [cm] = 19.53045[g] 5. If the aluminum "spring" were pulled 3mm, would it break? a) No - b) Yes -> Correcta + ✔b) Yes -> CORRECT 6. If the plastic "spring" were pulled 3mm, would it break? - a) No -> Correcta + ✔a) No -> CORRECT b) Yes /*********************************************************/ @@ -227,23 +245,23 @@ **********************************************************/ 1. Which of these tasks is significantly dependent on high actuator bandwidth (frequency at which actuator can work well)? Todas no son correctas. - 2, 3 y 4 -> Incorrect - a) High speed pick and place - b) A self-driving car making a passing maneuver -> Correct - c) A robot arm picking up a fragile object -> Correct - d) A legged robot catching itself after a stumble + 2, 3 y 4 + ✔a) High speed pick and place -> CORRECT + b) A self-driving car making a passing maneuver + c) A robot arm picking up a fragile object + ✔d) A legged robot catching itself after a stumble -> CORRECT 2. The speed torque curve establishes a relationship between these two physical properties in electric motors. Since power is the product of torque and angular speed, where does maximum power occur? a) At stall (no speed) b) At 1/4 no-load speed - c) At 1/2 no-load speed -> Correct + ✔c) At 1/2 no-load speed -> CORRECT d) At 3/4 no-load speed c) At no-load speed 3. Torque in an electromagnetic actuator is proportional to current by the constant Kt ( in Nm/A, often specified by motor manufacturers). The dominant mode of wasted energy in these actuators is due to Joule heating which scales with current squared. Where does maximum wasted energy occur? - a) At stall (no speed) -> Correct + ✔a) At stall (no speed) -> CORRECT b) At 1/4 no-load speed c) At 1/2 no-load speed d) At 3/4 no-load speed @@ -253,5 +271,5 @@ a) F=bx−k(x0−v) b) Fx=v(b+k)+x0 - c) F+bv=k(x−x0) -> Correct + ✔c) F+bv=k(x−x0) -> CORRECT diff --git a/README.md b/README.md index 9adaf17..50a89ae 100644 --- a/README.md +++ b/README.md @@ -1,3 +1,5 @@ Robotics Mobility -This is the documents from the Coursera Robotics Mobility - UPenn. \ No newline at end of file +This is the documents from the Coursera Robotics Mobility - UPenn. + +Including Every Week's Video and quiz's answer.