hi,
Let me introduce myself first. I am Bjorn lastyear student ingeniering for elektronics from the KDG group at Belgium and my project is to let the biped scout walk with accellerometer and gyro meter with the inverse kinematics method. On top of that we are going to place a camera wich can determe a little ball in a defined area where the robot has to walk too. the third part is to add 2 arms to the robot, in other words add 10 more servos. so the robot has to be modified. For the moment we are using the Hitec analog servos HS-645MG. But what we soon realised was that the servos are off with 15 degrees when heavy load are applied. Thid offset is very unwanted so are willing to replace these servos and use then for the robot arms. Now my question can anybody garantee that the Digital HS5645MG or better will stay at his place and that they can carry this load ( arms 800g, battery 400g, elektronics, 300g ). can anybody give me some advice?
I’m thinking of buying 10 HSR 5980. But they draw a little bit more current . Now a battery of 7.2 V 4000mah will this suffice. What do you guys think?
Buy the HSR-5980 servos. You will get better performance than the HS-5645 servos.
When developing your algorithms, don’t worry about power. Use a power tether to a bench top power supply. Find the battery you want to use and put it on the robot so you develop the code with the proper weight on the robot. When everything is working, then use the power on the robot.
I would suggest that you look at the Lithium Ion batteries. More expensive, but less weight.
Inverse kinematics is going to be a tough one to get working, especially finding the proper microcontroller that can handle the numerical analysis.
I would suggest that you get a wireless data link between the robot and a computer to develop your inverse kinematics. The wireless link will transmit all of the servo commands to the SSC-32, and relay back critical sensor information. The PC will control the walking. Once you have developed the walking routines on the computer, then you should look for a microcontroller that can do the math.
thanks I can use this information. jup we now the inverse kinematics is going to be a thouph one, but I have a hole group of students under “my command” and they will help me find a proper algorithm. We use a wireless rs232 link to matlab.
because the whole system should run embedded we kinda made a microcontroller bord with the DSP PIC33lf256 from microchip. the only thing this baby has to do is calculate the inverse kinematics, now I hope he is fast enouph.
can anybody confirm that the HSR 5990TG can be mounted on the Biped scout? Isn’t the feedback mechanism in the way if you want to mount the servo in the servo erector set?
The inline pivot bottom case can be removed and replaced with a stock one that comes with the servo. Alternately the ASB-04 can be modified by enlarging the bearing mount hole to accomodate the integrated pivot point.
The 5980 and the 5990 servos come with two choices of servo bases. One base has the pivot, the other base is flat like the regular servos. So if you want to use the bearing on the servo bracket, you can just change the base of the servo.
The robot is controlled by a PID regulator. Its not that incredible but we’ve had a lot of trouble with the electronics and we’ve waited for the servo’s for so long (financially aspect ). The next step would be increasing the performance of the PID and mounting 4 FSR’s under each feet for better stabilization.
Best regards
PS: don’t pay any attention to the first comment on youtube. Its just a friend of my .
Is it posible that when you use the plastic standard servo horn instead of the metal horn that the mechanic can bent. so it would be impossible to make the robot walk or did I made a mistake ? the problem I’m having is when the robot walks and lift its feet the machanic seems to have a problem holding the initial position, it just bent and the feet is back on the floor.
bjorn, I don’t have much experience with the plastic servo horns, since I have never used it on my bots, but if your feet are going limp, make sure you check your power and make sure that you have plenty of power to feed the servos. When the biped scout is trying to walk, it draws quite a bit of current. I had a problem with my servos going limp on me in my hexapod because under an extreme load, all 18 servos were drawing too much power from one battery pack so the voltage dipped below the cut-off of the regulators on my botboard, causing my botboard to reset…
The new, all-aluminum leg biped scout is a thing of beauty, I have one of my own. It’s in pieces right now, but I’m planning on restoring it with a full set of HSR-5990TG…
They will be mounted in each corner of each foot. So we will have a nice representation of the balance and total weight. The FSR’s will detect an unbalance ( linke a push, witch means the robot should step in the same direction of the push) or detecting a surface that’s not parallel with the earth.
I think I will interface it with an extra small microcontroller to perfrom the AD conversion so you can get the values trough I²C.
can anybody garantee that the Digital HS5645MG or better will stay at his place and that they can carry this load ( arms 800g, battery 400g, elektronics, 300g ). can anybody give me some advice?
