Walking robots – Quadrapeds! Hexapods! Octobots! This is an expansion upon the I, Robot blog. As my foray into the world of robots has expanded, so I have become more interested in the possibilities of a hexapod over the 4WD robot.
An awesome hexapod from PhantomX Hexapod Phoenix Code. See the section The PhantomX, below
PhantomX/Hexacopter hybrid: Hexapod Quadcopter.
The libraries are on github.
LinksMotion.com: Phoenix Hexapod. 2 cell LiPo Battery
They mention that it has two Castle BECs. For more information, see Power Up! However, here is one in a cool 4WD car:
“What’s in the box?!?!”
An actual spider! A recent purchase by the chap from MythbBusters:
From howtomakearobot.us, a terrible video, but a dirt cheap hexapod. Unfortunately all of the links to the blueprints are broken (scroll to the bottom of the page). Pointless..!
Try the 18DOF Black Hexapod Robot Spider Kit for Arduino Raspberry Pi PICAXE, for £35. It is made of PLA (plastic) not aluminium, and does not have many mounting holes in the top, and the seller will not add more.
The vastly superior, 1Set Six 3DOF Legs Alum Alloy Hexapod Spider Robot Frame Kit DIY for Arduino, for £46. Made from aluminium and has a lot more mounting holes.
Or a silver one, of more or less the same design, that comes with aluminium servo horns, 18DOF Aluminium Hexapod Spider 6 Leg Robot Kit wi Servo Horn Ball Bearing-Silver, for £59
The cheapest, and lightest at 308g (with servos) is the 1 Set 18 DOF Six Feet/Leg Hexapod4 RC ArrivingSpider Black Robot Frame NO SERVO, for £13.84, or cheaper still 1 Set 18 DOF Six Feet/Leg Hexapod4 RC Mini Spider Schwarz Robot Frame NO SERVO, for £11.39
With the servos (SG90), 1 Set 18 DOF Six Feet/Leg Hexapod4 RC 99 UK Spider Black Robot Frame+18 Servos for £48.90
Now, SG90s are a pound each, so £18 for the servos and £14 for the hexapod is £32, so it is cheaper to buy the kit and the servos separately.
A simpler 12DOF, Hexapod Six Feet Robot Spider Arduino DIY Robot KIT 12DOF NO SERVOS, £13.87
There is also a 6DOF, or rather 12DOF, hexapod, DIY Six Feet Robot 6-Legged 6DOF Hexapod4 Spider Robot Frame Black, £28
This model from Lynxmotion Aluminum Hexapod Body Kit – Full Size (Brushed), for $25, has a interestingly simple construction
Unfortunately the Alpha Hexapod product link, given above, is, now, dead, but the Alpha Hexapod looks very similar to, and uses the same servos as, the Robo-Soul CR6, 18DOF Robo-Soul CR-6 Hexapod Robotics Six-legged Spider Robot Kit / LD2015 Servo, £229.61. Uses LD-2015 servos, which are similar to MG996, but not identical – See Service please!.
So, for each hexapod type, some costs are fixed, such as the electronics (the same Arduino and control shields and code will be used regardless) and the power (although power requirements will vary, somewhat, depending on the servos used). However, the main variation in cost is the kit and the servos. So,
Body Kit cost = £14
18 x SG90 @ £1.15 = £20.70
=> Total £34.70
18 x MG90 @ £2.11 = £37.98
=> Total £51.98
Body Kit cost = £35
18 x MG996 @ £3 = £54
=> Total £89
Body Kit cost = £46
18 x MG996 @ £3 = £54
=> Total £100
So, it can be seen that the prices soon mount up, due to the large number of servos required. The hexapod4 is a third of the cost of the aluminium model
Comparing this with the 4WD car (See I, Robot):
Chinese = £12
PLA = £25
Aluminium = £42
Interestingly, the cost difference is proportionally less as the quality goes up, so the Chinese 4WD car is a quarter of the cost of the hexapod equivalent, the PLA 4WD car is between a third and a quarter, and the Aluminium 4WD car is just under a half of the cost of its hexapod equivalent. Obviously, the hexapod is more manoeuvrable, although, it may not been as rugged.
The superlative hexapod:
The PhantomX is $1199!
However, it is the AX-18A actuators, which are $94.90 each => $1708.20 ($79.08 each ($474.50 for 6 pack) => $1423.50), that bumps up the price. Surely it can be done cheaper, using Chinese clone servos. The Dynamixel AX-12A Robot Actuator is cheaper, at $44.90 => $808.20 ($37.40 each ($224.50 for 6 pack) => $673), but slower. Dimensions here.
SR518 robot Digtal metal servo 360° rotation 18kg 6-12V, $35.30 => $635
While looking at the BOM, I saw this line:
21 Dynamixel MX-28T 220/eachthusatotalof4620
It seems Herkulex DRS-020X Series are similar:
One can buy them for 118,94 € here:
It is a great difference!
The DRS-010 series is even cheaper (nearly half) but the difference seems to be the angle amplitude. Is it mandatory everywhere to have such an amplitude?
DRS-0201 in stock on robotshop.com.
There is a discount price of 116.64/eachwhenbuying25ormore.35.34/each for DRS-0101 over 25 pieces.
On FranceRobotique.com 105€/DRS-0201 and 33€/DRS-0101.
I imagine using HerculeX servos would imply redesigning structure pieces.
For the difference between 0101 and 0201 are you sure it is amplitude ?
I read a half torque for 0101, and brush dc(01) vs coreless dc(02).
I’ve found the SpringRC SR-518 knock-off of the AX-18s on ebay (e.g.: http://bit.ly/1j0nDPL99 ). Has anyone used these servos? They are supposed to be “Dynamixel compatible”. Could this be a cheap option?
I’ve found some documentation on the SR-518 that includes a lot of great information about their communication protocol. It is half duplex RS485 (4 wire), just like the Dynamixel RX and EX series. So, not great news, but not terrible news, either.
There is also a whole chapter on creating a servo controller with the AVR SCM, including schematics, Eclipse screen shots, and sample c source code.
I tried to attach it, but apparently I’m too new to do such a thing
MX 28/64 servos
Already available to buy:
- @loicf link to Herkulex Series:
- @jamma link to the SpringRC SR-518:
- @jgrizou link to Turnigy Motors:
There’s also the MX-12W. Same strength as the AX, but probably a lot smoother:
We can consider it is a direct replacement of AX-12W.
I confirm the MX-12W are too weak to be in a “child sized” robot.
we have new servos MX28AT MX64AT with advanced heat factors.
After searching for a cheaper servo, I believe I may have found it. Has anyone tried the Robostar SRS-3216htg? They may be a good substitute for the MX-28. There is also the SRS-5314Htg as well. They both can be found at the Hobbyking web site. Here is a link:http://www.hobbyking.com/hobbyking/store/__64645__RoboStar_SBRS_5314HTG_280_Digital_Metal_Gear_High_Voltage_Robot_Servo_53_1kg_0_14Sec_81g.html
SCS15 from Feetech
I bought this servo SCS15 from Feetech for my first robot, it is 15kg-cm torque, with feedback, daisy chained.and the price is really attractive. this lady helps me a lot.
Rosita,Skype: sales018feetechrc,Email: email@example.com(agreed)
Looking at the specifications of the servos:
|Stall Torque*||18.3 kg·cm
1.8 Newton Meter
|Size||32 x 50 x 40mm|
|Operating Angle||300° or Continuous Turn|
|Max Current||2200 mA|
|Standby Current||50 mA|
|Operating Temp||-5°C ~ 85°C|
|Protocol||TTL Half Duplex Async Serial|
|Module Limit||254 valid addresses|
|Com Speed||7343bps ~ 1Mbps|
|Load Voltage Feedback||Yes|
|Input Voltage Feedback||Yes|
|Material||Plastic Gears and Body|
|Manual Download||AX-18A manual|
3-Pin TTL DYNAMIXEL Compatible Controllers
*Stall torque is the maximum instantaneous and static torque. ROBOTIS recommends that your robot or project uses 1/5 or less of the stall torque to create stable motions.
6 x Bioloid Frame F1
12 x Bioloid Frame F2
6 x Bioloid Frame F3
All are $1.50 each => $36
Metal Bioloid F1 are $4.95
Metal Bioloid F2 are $4.95
Metal Bioloid F3 are $4.95
Total metal cost = 24 x 5 = $125
F4 also available, but not necessary. Also, it is difficult to see where the F3 is used, as the leg seems to be: Actuator>F1>F1>Actuator>F2>Actuator
That just leaves the three body plates and the leg, see assembly guide.
- Hexapod Body Top Plate
- Hexapod Body Bottom Plate
- Hexapod Top Deck Plate
- Hexapod Body Side Plate x 2
- Tibia Side Plate
- Foot Plate
- Back Toe Plate
- Front Toe Plate
I fired off an email to trossenrobotics to clarify a few points:
Can the Arbotix-M Robocontroller can control other servo types, i.e. the TowerPro mg996? or only the DYNAMIXEL servos which are listed in the compatibility list?I know that it states that the Commander and the Robocontroller do not support XBee pro, (why is that by the way?), and all of the photos show it being used with a XBee Series 1 module, but can the Arbotix-M Robocontroller/Commander accept XBee Series 2 or 2B? If so, which XBee protocols do they support?Also, the prices for the barebones kit for the quadbot, hexapod and octopod are quoted at $219.99, $269.99, $299.99 respectively. However, these kits include plastic bioloid brackets, I believe. How much are the barebone kits if all of the bioloid brackets are metal, instead of plastic.Regarding the servos, must DYNAMIXEL servos be used to build the octopod, or hexapod, or can MG996 servos be used? Would they fit?Also, are the robots legs, feet, body plates, etc. made from plastic or aluminium? It does not say in the description and I can’t tell from the photos.
The arbotiX-M can control standard RC Hobby servos. It has voltage support for 4 servos (i.e. you can power them from a separate power terminal). You can control more servos though you may need to do your own power wiring and this will depend on the servos you are using.The lack of XBee pro support is due to footprint (a xbee pro will not fit) and power (xbee pros need more 3.3v power than our regulator supports). It is possible to attach a board like the XBee explorer to the serial pins on the FTDI port on the boardThe connections are a simple serial connection, so any bee type device that sends 5v ttl serial will work. We have our own protocol (the commander protocol) that works on the byte-level over serial.None of the kit is currently metal – it is all made of acyclic. . We are in the process of updating the kits for metal (including metal body plates and tibias), but I don’t have a date right now. Keep in mind that the cost of the kit will also be increased.The kit is designed for AX-12/18 servos and other servos will not fit.
See also, I, Robot, for controller list (need to join the two really).
ArbotiX-M Robocontroller, for £38.80, only take non-PRO. Not sure if it is compatible with XBee Series 2.
Costs of Kits
- Barebones $269.99 (plastic)
- Barebones $X?X.?X (metal)
- 42 pieces total without the Bioloid brackets
- 3 Body parts
- 2 Side plates
- 1 XBee clip
- 36 pcs for the 6 legs
- 24 Bioloid brackets
Servos AX-12A $1199.95,
Servos AX-18A $1994
Sussex Ironcraft Ltd
- Tel: 01273 927100
- 31B Avis Way, Newhaven, BN9 0DJ
Quadra Pod Robot
Four Feet Robot 4-Legged Hexapod3 Mini “Spider” Arduino DIY Robot KIT NO SERVOS, for £6.66 +£3.20 => £10
Servos cost reduced
- 12 SG90 x £1 = £12
- 12 MG90 x £2 = £24
A simpler arm, like the GoPro camera robot arm which only offers 2DOF, is the 3 DOF Mechanical Arm Claw 3 Axis Steering Gear Bracket without Gripper Robotic U, for £8.70
Here is the kit of parts. How is differs from the 2DO GoPro bracket, is the addition of the short brace.
As it has 3 servos, then it could be used as a weighty hexapod‘s leg. The only issue is would the body plate be strong enough to hold 6 legs such as these? 6 legs at £8 each is £48.
Legs, Lynxmotion Robot Leg “B” Pair (No Servo) RL-02, for $7
See this leg for its compactness, strength, accuracy to life, form, use of OU brackets, Lynxmotion Aluminium Leg Pair (No Servos) (Black) THLEG4-BLK, for a ridiculous $111,
However, note its make up.
- LU 1.14
- OU 1.19
- OU 1.19
- MF 1.85
- Total: £5.40
Adding a LU or SU would be easy, and maybe two extra MultiFunction brackets are used.
There’s Lynxmotion Aluminium Leg Pair THLEG3-BLK (No Servos), for $80.35
Again note the simple, and cheap, construction,
- 2 MF £1.85
- LU £1.14
- OU £1.19
- MF £1.85
- Leg £1
- Total: £6
- 2 MF £1.85
- 2 LU £2.28
- 1 leg £1
- Total: 5.14
- 2 MF £1.85
- 2 SU £2
- 1 leg £1
- Total £4.85
Or Lynxmotion Aluminum 2DOF Leg Pair (No Servos) 2DOFA-BLK, for $51, only 2DOF!
- 2 MF 1.85
- 1 OU 1.19
- 1 leg £1
- Total: £ 4.04
Hands as feet? Lynxmotion Robot Hand – B (no servos) RH-02, for $10
The hexapod in this video has 4DOF per leg. The leg design is quite versatile.
Back and Front legs
Or, Lynxmotion Tubing Foot Contact Switch Kit (Pair), for $9
Touch contact switch eBay, Car Helicopter Crash Collision Sensor Switch Module Robot Model For Arduino, £1.00
- High strength, Non-friable and Non-conductive
- Designed to fit a variety of sensors, controllers and power switch
- It also has a servo mounting hole which fits for Pan/tilt Kit
- Thickness: 1.6mm
Body Plate Plans
Here are some body part chassis, for quad and hexapod. I can’t find any 8 legged chassis though. From My first robot : a quadruped with 3 DOF by leg, PVC plate (dimensions 180 x 180 mm, 5 mm of thickness) :
So, if four legs is 160mm (20mm in from edge), shoulder to shoulder, add another plate but 160mm apart, total = 3 x 160 = 480mm.
The silver Aluminium Hexaped is roughly 200mm in length, Body shell size: 17.5*15.5cm(L*W)).
So, if four legs is 165mm (5mm in from edge), shoulder to shoulder, add another plate but 165mm apart, total = 3 x 165 = 495mm.
So, deducing from this, legs’ shoulders can be 100mm – 200mm apart. So, for a 8 legged robot, body length is 400mm – 800mm, width 150mm – 200mm.
Lynxmotion Symmetric Quadrapod Body Kit – Mini QBK-02, for $19.95, as used in Arduino Quadruped Robot
- Height = 2.125” (1.875” Standoffs) (53.975mm) (50mm in standoffs)
- Length = 5.5” (Body) (139.7mm)
- Width = 5.5” (Body) (139.7mm)
- Length = 5.0” (Axis points, End to End Leg) (127mm)
- Width = 5.0” (Axis Points) (127mm)
So, if four legs is 140mm, shoulder to shoulder, add another plate but 140mm apart, total = 3 x 140 = 420mm.
There is the Lynxmotion Phoenix Chassis Kit PHBK (Brushed), for $11.95, which is the body of the silver hexapod
There is the Lynxmotion Aluminum Hexapod Body Kit – Full Size (Black), for $27
- Height = 2.125” (1.938” standoffs) (53.975mm) (50mm in standoffs)
- Length = 14.000” (Body) (355.6mm)
- Width = 3.500” (Body) (89mm)
- Length = 6.000” (Axis points, end to center leg) (152.4mm)
- Length = 12.000” (Axis points, end to end leg) (304.8mm)
- Width = 6.250” (Axis points) (158.75mm)
There is a smaller version, Lynxmotion Hexapod Body Kit – Mini HBK-01, for $24.95
- Height = 2.125″ (1.875″ standoffs) (53.975mm) (50mm in standoffs)
- Length = 10.500″ (Body) (26.7mm)
- Width = 3.000″ (Body) (76.2mm)
- Length = 4.250″ (Axis points, end to center leg) (107.9mm)
- Length = 8.500″ (Axis points, end to end leg) (215.9mm)
- Width = 4.250″ (Axis points) (107.9mm)
An ant, Lynxmotion Electronics Carrier – Ant-Style EC-01 for $9, in plastic
- T-Rex, Lynxmotion Aluminum T-Hex Body Kit (Black), for $73
- From RobotShop, Lynxmotion Aluminum T-Hex Body Kit
Product Code : RB-Lyn-325, £39.88
- On eBay, Lynxmotion Aluminum T-Hex Body Kit (Black), £66.46 + £5.90
Here is a thread from 2007 about some rumoured octopod chassis, Octopod Chassis
Another thread here, Octopod | Keith Elliott’s Personal Site, from two hexapod4.
Another tread here, about the OCTCHASSV000, WALKER8 – An Octopod Project, comes with a video
Also about the OCTCHASSV000, Mini Custom Octapod Project. The chap has built two, with a very nice chassis:
With a chassis made with four CM5 Bioloid parts,
the Octopod, not Hexapod! looks good,
The NASA (JPL) RoboSimian, can crawl, walk and wheel itself along.
This is the design document for the RoboSimian.
The Robosimian has 6DOF or 7DOF per leg. The leg design is quite impressive.
Humanooidbot with wheels
Another type of transformerbot. Using Innovati parts, this bot can walk, and drive