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Servo benchmark stress test

benchmark stress test comparison failure Vigibot

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#1 firened


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Posté 25 juin 2022 - 02:26

servo benchmark

goal: find robust servo models for a Minus-Type robot, in the hopes of extending time between servo failures and repairs. A per piece price of up to 20$ may be acceptable (N20 Pololu motors are also in that range). Minus-Type uses Micro Servos, also called 9g or sg90.

tested are the following servo models:

1) DIYMore SG90, plastic gear, 1$: recommended by Vigibot. are very quick which makes for a comically fast head nodding that people find hilarious. used on most of my robots (not WalterJakob's pan-tilt), personal failure rate is pretty high.

2) DIYMore MG90S, metal gear, 3$: had servos in the past that were DOA or didn't work on the lower battery voltage, unfortunately can't remember the exact reason.

3) TiankongRC TS90A, plastic gear, 270°, 3$

4) Doooman Hobby DM-S0090MD, metal gear, 270°, 6$

5) DFRobot DS-S006L, plastic gear, 9$: has a clutch to protect internal gears.

6) FiTec FS90MG, metal gear, 6$

7) Spektrum A330, plastic gear, 18$

8) Futaba S3114, plastic gear, 20$: "sub-micro" servo doesn't fit the current 3D printer files, requires small adjustment.

9) HiTec HS-55+, plastic gear, 20$

10) HiTec HS-5055MG, metal gear, 30$

11) HiTec HS-65MG, metal gear, 30$
↓ See conclusions or table "benchmark table.xlsx" for servo failure times.

test tries to simulate real world usage, common scenarios:

• to work with Vbat voltage 3.3V - 4.2V

• usually low weight/momentum movements (camera is pretty lightweight)

• people may accidentally hit the robot

• robot may drive into walls or objects with a servo absorbing the hit

• servo may want to move into an object and be limited by it

stress test setup:

pre-test #0: power from 3.3V and check if servo is even functional (most servo specifications state a minimum operating voltage of 4V). stop movement with hand, to check if it stops immediately / gets stuck.

main test #1: power from 3.3V, move back and forth (90° - 0°) automatically (eg 1 cycle every 6s to keep temperature low), no weight attached. from time to time force into obstacle (180° position can't be reached) to simulate real world interaction. let run every night and check how many minutes they last before they stop working.

27.5.22: ran test #1 for 2400min (actual movement: 400min), 1 cycle (to 0° and back to 90°) every 6s, no failures.

-> replaced with 10A 3.3V power supply. increased speed from 1 cycle every 6s to 1 cycle every 2s. now movement from 3 servos overlap. can still be doubled. temperature IR meter: room = 27°C, servo avg = 35°C, servo max = 37°C.

28.5.22: ran test #1 for 480min (actual movement: 240min), 1 cycle every 2s no failures.

-> increased speed to 1 cycle every 1s. movement from 6 servos overlap, maximum possible. temperature IR meter: servo avg = 42°C, servo max = 46°C

29.5.22: ran test #1 for 800min (actual movement: 800min), 1 cycle every 1s,

-> divided runtime value by intensity to "actual movement" value.
Fichier joint  VID_20220606_211516.mp4   13,93 Mo   18 téléchargement(s)
Conclusion for Botkins / Minus-Type Robot:

6 servos had good behavior and more than acceptable runtime until failure.

Metal Gears:

• DIYMore MG90S: Okay

• FiTec FS90MG: Okay

• Doooman Hobby DM-S0090MD: Okay (Pan 270°: cable fatigue!)

Plastic Gears:

• DIYMore SG90: Okay

• DFRobot DS-S006L: Okay (auto-revert would need some testing)

• TiankongRC TS90A: Okay (Pan 270°: cable fatigue!)

not recommend servos:

• Spektrum A330: No (failed early)

• Futaba S3114: No (.stl doesn't fit)

• HiTec HS-55+: No (Slow)

• HiTec HS-5055MG: No (3.3V unsupported)

• HiTec HS-65MG: No (Slow)

See table "benchmark table.xlsx" for servo failure times.

Fichier joint  benchmark table.xlsx   10,69 Ko   26 téléchargement(s)

Modifié par firened, 25 juin 2022 - 06:54 .

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