torque analysis: leg servos

TORQUE ANALYSIS: LEG SERVOSServo Information

Leg LayoutServo Type Dimensions Max

Torque “Tmax” (oz-in)

Weight “W” (oz)

High Torque (HT)

1.57 x 0.78 x 1.45

417 2.18

Low Torque (LT)

1.57 x 0.78 x 1.45

124 1.190.78’’

5.22’’

Hip Lift: 1 HT Servo

Knee: 1 HT Servo

Ankle: 2 LT Servos

Hip Torsion: 1 HT ServoAssumptions

-Link weight acts at center of link-Links made of Aluminum ρal = 15.6 oz/in3

-Link Thickness: t=1/16’’-Links are the width of the servo and cover top-Links are on both sides of servos

10.72’’

TORQUE ANALYSIS: HIP SERVOMax Torque Condition on Hip Servo when leg fully extended and // to ground

F1 F2

Tmax+

F1= ρal*t1(2*L2*W1+(L2-1.25)*W2)F1=15.6*0.0625(2*5.22*0.78+(5.22-1.25)*1.45F1=13.90 oz

F2= ρal*t1(2* (L3-L2) *W1+(L3-L2-1.25)*W2)F2=15.6*0.0625(2*(10.72-5.22)*0.78

+(10.72-5.22-1.25)*1.45F2=14.37 oz

S1 S2 S3

S1=S2=S3=SHT = 2.18 oz S4=2SLT= 3.88 oz S4

L1L2

L3

L1= 0.78’’L2=5.22’’L3=10.72’’

𝑇𝑚𝑎𝑥=(𝑠2∗𝐿1 )+(𝐹 1∗(𝐿1+ 𝐿2−𝐿12 ))+(𝑠3∗𝐿2 )+(𝐹 2∗(𝐿2+ 𝐿3− 𝐿22 ))+(𝑠¿¿4∗𝐿3)¿

𝑇𝑚𝑎𝑥=(2.18∗0.78 )+(13.90∗(0.78+ 5.22−0.782 ))+ (2.18∗5.22 )+(14.37∗(5.22+ 10.72−5.222 ))+(3.88∗10.72)

𝑇𝑚𝑎𝑥=210.90𝑜𝑧−𝑖𝑛 Factor of Safet 𝑦=417210.90=1.98

TORQUE ANALYSIS: KNEE SERVOMax Torque Condition on Knee Servo when Thigh // to ground & Shin ┴ to ground

L2

Additional Assumptions-Each Arm consists of 1LT & 3 HT Servos-Neck has 2 LT Servos-Hip Joint has 3 HT Servos-Arm Links are same as leg links (conservative)-Torso + Electronics weigh 4 lbs (64oz)-Each Knee has to lift ½ weight of robot--Upper body leaning such that half weight is at thigh and other half is halfway b/t thigh and knee

L3-L2

𝑊 𝑟

2 F1

+Tmax

L2=5.22’’L3-L2=5.5’’

F1=6.76 oz

Wr = 2Warm+Wneck+2Whip+WtorsoWr=2*(1LT+3HT+F1)+2LT+3HT+48Wr=2(1.94+3*2.18+13.9)+(2*1.94)+2(3*2.18)+64) Wr= 128.54oz

𝑇𝑚𝑎𝑥=𝑊 𝑟

4∗𝐿2+

𝐿22 (𝑊 𝑟

4+𝐹 1)

𝑇𝑚𝑎𝑥=128.544

∗5.22+ 5.222 ( 128.544 ∗+13.90)

𝑇𝑚𝑎𝑥=258.85𝑜𝑧−𝑖𝑛 1.61

TORQUE ANALYSIS: PUSH UPServo Information

Servo Type Dimensions Max Torque “Tmax” (oz-in)

Weight “W” (oz)

High Torque (HT)

1.57 x 0.78 x 1.45

417 2.18

Low Torque (LT)

1.57 x 0.78 x 1.45

124 1.19Assumptions-Link weight acts at center of link-Links made of Aluminum ρal = 15.6 oz/in3

-Link Thickness: t=1/16’’-Links are the width of the servo and cover top-Mass of 2 lbs at chest used to estimate internal electronic components and hip mass of 1 lb used to estimate battery

Push-up Layout

F

F

+O

182mm

118mm

201mm

118mm

140mm

120mm

140mm

120mm

120mm

TORQUE ANALYSIS: PUSH UPMax Torque Condition on Hip Servo when leg fully extended and // to ground

F1 F2

To+

F1= ρal*t1(2*L2*W1+(L2-1.25)*W2)F1=15.6*0.0625(2*5.22*0.78+(5.22-1.25)*1.45F1=13.90 ozF2= ρal*t1(2* (L3-L2) *W1+(L3-L2-1.25)*W2)F2=15.6*0.0625(2*(10.72-5.22)*0.78

+(10.72-5.22-1.25)*1.45F2=14.37 oz

S1 S2

S1= 2*2.18 oz = 4.36 oz S2= 6*2.18 oz = 13.08 oz S3= 4*2.18 oz = 8.72 oz

M

L1L2

L3

L1= 182mmL2= 383mmL3=501mmL4=620mm

+(*) – (F * )

𝐹𝑎𝑡 h𝑠 𝑜𝑢𝑙𝑑𝑒𝑟𝑠=52.53𝑜𝑧Factor of Safet 𝑦=

417289.94=1.44

L4

S3

F

M=2lbs

, assume T=0 at o (moment balance)

F+(8.72*620))/620

T

STRESS ANALYSIS ARM LINK

STRESS ANALYSIS ARM LINK

ARM

ARM

ARM LINK DRAWING

STRESS ANALYSIS SHIN LINK

STRESS ANALYSIS SHIN LINK

STRESS ANALYSIS THIGH LINK

STRESS ANALYSIS THIGH LINK