Design and control a Prototype Humanoid ( Servos )

Lynxmotion Legged Robots
1

Hi,
im designing a small Biped Humanoid ( height of about 32 cms ) but im not sure what kind of servos use in the design ( analog/digital ). Im thinking in BMS-380 MAX.

Logically i need small servos ( pico, mini ) with a big torque. Anybody have a suggestion?

Thanks in advance…

2

This is a fairly common size for servo-based humanoid bots (30 cm == about 12 inches), which are usually built using standard-sized servos, rather than micros. The problem with micro servos is that as the scale goes down, the strength of materials and precision of assembly become more important.

My experience with micro servos has often been that the gears often just aren’t up to putting out a lot of torque, or withstanding much abuse, and “abuse” is a fairly normal state of affairs for a humanoid bot. The little baby servos just aren’t usually designed to take the kinds of loads experienced by a biped during normal operation.On top of that, I have heard many varying reports as to the quality of Bluebird servos, and their suitability to high-stress robotic applications. Some people find them to be fine, but I have seen more people saying that they weren’t happy with the results.

For general design purposes, you might benefit from reading a number of the postings here in the “bipeds” and “projects” forums, to get a feel for what others have done, the problems they have run into, and the solutions they have found. The general consensus seems to be that the Servo Erector Set brackets, combined with some good, high-quality servos that have worked well for others result in a stable, strong robot that can be reconfigured at will, and withstand both normal and a good bit of abnormal use. Many people have learned that that trying to cut corners and save a few bucks here and there on cheap servos and the like end up costing more in time, money, and heartache, when you have to disassemble your robot repeatedly to replace stripped gears and/or blown servos, than it would have cost to have just gone with good, high-quality servos in the first place.

3

thank you very much for your quick answer Seamus.

I want design the biped robot with high quality components and materials ( the cost is not a problem ). I want use fiberglass or carbon materials instead aluminiun but i need a very good mini servo for soft movements and big torque.

Im looking the openservo project but are for standard servos ( big servos for my project ).

Mendroid

4

If money isn’t a problem, I’d research existing high quality prebuilt bipeds, and then modify them into what you need.

5

Hi Zoomkat,

i know that i can research or modify an existing biped but is NOT fun!!! :wink:

I continue searching digital small servos for my project. If anybody can help me wit your experience are wellcome.

Thanks in advance…

6

Hi again,

what about Hitec HS-5245 MG ( DIGITAL mini servo )?

Operating speed: 0.15 sec @ 60° at 4.8V
Torque: 61 oz-in (4.4 kg-cm)
Weight: 1.12oz (32g)
Length: 1.27" (32.4mm)
Width: 0.66" (16.8mm)
Height: 1.21" (30.8mm)
Wire length: 12" (305mm) approximate
price: 43 - 50 euros

but…

**similar digital mini servo smaller???

Thanks in advance**

7

I guess if you use carbon fiber you could use micro servos, however, the weight of the servos alone can add up and the ankle servos is going to be the “HOT” spot, these servos are going to have the greatest stress point with a bot with a high center of gravity. It can be done because you can buy a micro servo biped that uses plastic brackets but it’s fairly short so the center of gravity is much lower than a standard servo sized biped.

This biped uses proprietary micro servos:


TOMY Omnibot 2007 i-SOBOT Humanoid Robot

8

Hi SN96, thanks for your answer…

  My idea is build an ( small ) biped robot like SILF-2 ( Mini DC Motors ) or HR-2 ( BMS Max Servos ) with high quality components, fiberglass or carbon and a good design ( Linux inside ). Im trying to found micros or mini servos with high torque and high speed in order to have soft movements.

Anybody knows more projects similar?

Thanks in advance…

9

The Open Servo can be applied to ANY size servo as long as you can fit the electronics board into the case, or even standard motors. The new v3 Open Servo boards are about 1/2 the size of the v2.x boards.

8-Dale

10

Hi again,

any idea or some experience with this servo?

Manufacturer: Dynam
weight:7g
Torque:4.8V 1.6kg-cm
Speed:4.8V 0.1sec/60°
Size(mm): 21.8×11×19.8

Due to the size i cant use openservo to convert in digital servo. Any hack for this servo?

Thanks in advance

11

I have no experiance with this servo and hacks for it might be hard to come by because it’s not as popular as the other well known servos.