Avneesh AgarwalPuneet SinghVikas Dhiman

Under the guidance ofProf. H.O.Gupta

EED, IIT Roorkee.

ObjectiveHow we achieved our objective?1. Walking Algorithms2. Mathematical Concepts3. Design of 12 Degree of Freedom Biped4. Design of 4 Degree of Freedom Biped5. Controller Design6. Fabrication7. Testing and DebuggingWhy Biped Robots?ApplicationsObjectives Achieved and Future Aspects

The main objective of this project is to design and construct a biped robot that has the ability to walk forward on a flat plane.

There are three secondary objectives to be achieved in order to achieve the main objective stated above. The three secondary objectives are :◦ To design and construct the frame and actuators of the robot. The

parts needed are to be decided, purchased, fabricated and assembled.

◦ To design the electronic circuit of the robot. The controller circuitry and microcontroller programmer circuit are to be designed. The circuits are to be fabricated and tested for reliability.

◦ To design and program the controller of the robot. A program to implement the walking gait of the robot is to be written and loaded into the microcontroller.

Zero Moment Point (ZMP) locomotion ◦ At every instant there is no moment (torque) in

lateral or forward direction i.e. body is in equilibrium.◦ Can perform complex maneuvers like turning, stair

climbing etc.◦ E.g Honda Asimo (COT=3.2 J.N-1.m-1)

Dynamic Walking◦ Leg motion is made to imitate inverted pendulum.◦ Very energy efficient but not able to produce

complex maneuvers.◦ E.g. Cornell Biped(COT=0.2 J.N-1.m-1)

Coordinate Transformations DH coordinate system Direct Kinematics Inverse Kinematics

Step 1: Locate all joints and assign the joint axes, z0 - zn-1, so that each axis is coincident with the axis of revolution of the corresponding joint.

Step 2: Set the origin at a convenient arbitrary point on the z0 (base frame) axis. Chose the x0 and y0 axes so that they form a right-handed co-ordinate frame with z0.

For each remaining joint (joints i -> n-1), re-iterate steps 3 - 5.Step 3: If the joint axis, zi, intersects the previous joint axis, zi-1, at a unique point, this

point becomes the location for the origin of the joint. In the case of collinear axes, the origin is located at the joint.

Step 4: If zi and zi-1 intersect, the x axis, xi, lies in a direction normal to the plane created by the vectors zi and zi-1. For collinear axes, xi lies along the common normal of zi and zi-1.

Step 5: yi now forms a right-handed Cartesian co-ordinate frame with xi and zi.Step 6: A co-ordinate frame is assigned for the end-effector (assigned the label joint n).

zn is defined along the same axis, with xn and yn forming a convenient Cartesian frame.

Step 7: Evaluate the link parameters for each link:k = Angle of rotation from xk-1 to xk measured about zk-1. (Joint Angle)Dk = Distance from origin of frame Lk-1 to point bk measured along zk-1. (Joint

Distance)Ak = Distance of point bk from the origin of frame Lk measured along xk. (Link Length)k = rotation of zk-1 to zk measured about xk . (Link Twist Angle)

General Transformation of a coordinate frame w.r.t first frame = 0A1*0A2*…*0An

Mathematical Design DH Parameter for 12 Motor Biped Robot

Mechanical Design Mechanical Assemblies Mechanical Parts

Torque Simulation Results

Joint Angle (θk)

Joint Distance (Dk)

Link Length (Ak)

Link Twist Angle (αk)

0 0 .02 0

0 0 .04 -1.57075

0 0 .057 0

0 0 .057 0

0 .0095 .022 1.57075

-1.57075 -.0095 0 -1.57075

0 0 -.06 0

0 0 0 1.57075

1.57075 .0095 -.022 -1.57075

0 .0095 -.057 0

0 0 -.057 0

0 0 -.04 1.57075

0 0 -.02 0

DH Parameters for 12 Motor Biped Robot

Gait

Thigh

Leg

Foot

Hip

Ankle

GAIT Hip Upper Joint HIP

Thigh LEG ANKLE FOOT

Hitec Servo HSR5498SG

1-4 : LIFT ACTIVE LEG 5-9: SWING ACTIVE LEG 10-14: GROUND ACTIVE LEG 15-24: DOUBLE LIMB SUPPORT

PHASE

25-29: CHANGE ACTIVE LEG 30-34: LIFT ACTIVE LEG 35-39: SWING ACTIVE LEG

Mathematical Design DH Parameter for 4 Motor Biped Robot

Mechanical Design Mechanical Assemblies Mechanical Parts

Torque Simulation Results

Joint Angle (θk)

bi Joint Distance (Dk)

Link Length (Ak)

Link Twist Angle (αk)

0 .02 0 0 0

0 0 0 .0344 -90

0 0 0 .058 0

0 0 0 .0344 90

0 -.02 0 0 0

 Phase I: Lifting Active LegPhase II: Swinging Active LegPhase III: Grounding Active Leg

Phase IV: Changing Active Leg(Double Limb Support Phase) and Lifting New Active legPhase V: Swinging New Active legPhase VI: Grounding Active LegPhase VII: Double Leg Support Phase

◦ Servo MotorsFutaba S3003:

Dimension: 40 x 20 x 37mm Weight: 39.8g Output torque: 3 kg.cm

◦ Microcontroller & circuit elements Microchip PIC18F4550

Programming & Execution Board

Pulse width of 900-1900 microsec

Pulse width of 20 ms

+−

6 V DC Power Supply

There are basically three types of signal on the port pins.

Digital Outputs Digital Inputs Analog Inputs

Each port has three registers for its operation. These registers are:

TRIS register (Data direction register) (1-Input 0-Output)

PORT register (reads the levels on the pins of the device)

LAT register (Output Latch)

ADCON2

ADCON1

ADCON0

Objectives StatusThe main objective of this project is to

design and construct a biped robot that has the ability to walk forward on a flat plane.

Robot constructed can walk on flat plane surface.

1. To design and construct the frame and actuators of the robot. The parts needed are to be decided, purchased, fabricated and assembled.

Frame of 12-DOF and 4-DOF biped were designed. 4-DOF biped was fabricated. For this motors were purchased and fabrication material.

2. To design the electronic circuit of the robot. The controller circuitry and microcontroller programmer circuit are to be designed. The circuits are to be fabricated and tested for reliability.

Serial Port Programmer was constructed. USB programming and execution circuit was designed. We additionally interfaced a proximity sensor for obstacle detection.

3. To design and program the controller of the robot. A program to implement the walking gait of the robot is to be written and loaded into the microcontroller.

Microcontroller was programmed accordingly.

A biped robot would be able to move across uneven discontinuous terrain better than wheeled robots

Biped robot body can be made shorter along the walking direction as compared to multi-legged robots.

Common terrains like staircases are designed for bipedal walking.

Surveillance along difficult terrain Outer space exploration Land mine detection Nuclear Power plant Gas leakage detection in coal mines Can be used in rescue operations Can replace human worker in long term