From this listen, we are starting the trajectory planning of robot manipulators.
This is really interesting and exciting topic because it not only contains some math, but also it will
help us to do interesting things with robot manipulators.
So here are the topics that we have seen until today about robot manipulators.
We have seen kinematics of robot manipulators where we discussed forward and inverse kinematics of robot
manipulators.
Then we have seen dynamics of robot manipulators where we got orderly, the information about how forces
affect the position and orientation of robots manipulator.
Now we are considering trajectory planning of robot manipulators.
After that, we will see the control of robot manipulators.
The reason we will study trajectory planning first is that we want to first create trajectory that robots
will follow and then make robot follow it through some control algorithms.
Let's let's assume that we have given the task of picking a place where we take an object from starting
point and place it into the specified destination point.
So what are the steps that we have to follow to do the task?
We have to start the task planning where we try to specify the starting and destination point.
Then we are doing path planning where we identify the intermediate points that enable us to go to the
desired position without collision with obstacles and internal collisions.
So is that all?
Can we now control our robot and make it follow the calculated points and reach the destination?
Yes, indeed we can do, but we shouldn't do that because every robot has its own specification and
capabilities.
It depends on its multiple ability, actuator specifications and so on.
So we have to consider trajectory planning step also where we take time into consideration.
Also, namely, we have to determine the velocities and accelerations of robot manipulator at each point
we have.
We have to make robot follow the given paths not in the arbitrary way, but in a smooth fashion, because
robot manipulators actuators have velocity limits and torque limits, and we have to respect that.
So from that discussion discussion, you can somehow understand the difference between the path and
the trajectory.
Path is pure geometric description of motion where we just specify the points that and the factor has
to follow.
These points can be determined either in joint space or in operational space, and we don't take into
account time motion, namely velocity and acceleration.
However, in terms of trajectory, we have to take into consideration timing low in terms of velocities
and accelerations in order to provide smooth motion of robot manipulator.
Without such rotating actuators.
So let's summarize here why we need trajectory planning.
First of all, we want to avoid abrupt motions of robot manipulator because it is not only dangerous
for other objects near the robots, but also for the actuators of the robot joints.
We want to take into account the actuator velocity and torque limits in order not to pass these limits
and saturate actuators during reaching some destination point.
And last but not least, we want to go.
We want the coordination and synchronization of multiple bodies.
Namely, for example, the robot manipulator consist of six joints or seven beings in order to reach
the given point.
Some joints have to move shorter, while others longer.
We have to take this issue into consideration because we don't want some joints reach the desired configuration
faster than others and stop while other joints still moving.
We want them all to reach the final configuration at the same time and in a smooth way.
Here we are confronted with the issue of coordination and synchronization.
Finally, we can plan the trajectory for our robot manipulator in two ways, namely in joint space and
in operational or task space.
Both of these methods have their own advantages and disadvantages, namely when we plan the trajectory.
One of the key issues is obtaining collision free trajectory as obstacles are in task space.
We can consider obstacles in tasks based more easily so we can plan our trajectory in operational space
or task space.
However, after planning the trajectory, we have to execute it, but we cannot give the Cartesian coordinates
that we have calculated during Tusk Space Trajectory Planning Director to join us because we have to
convert them into joint space coordinates that joints can understand.
And as you know, this process includes inverse kinematic step, and we have to do that at each step.
You also know that calculating inverse kinematics is painful, so execution of task space trajectory
is slower than Joint Space Trajectory because during planning trajectory in joint space, we obtain
joint space coordinates and we don't need to.
The metrics, in order to feed these coordinates into the joint, so execution of joint space trajectories
is faster.
Additionally, we have advantage of taking into consideration of singularities during planning trajectories
in joint space.
Moreover, joint space trajectories are smoother than thrust space coordinates because we directly control
the actuators.
Another problem with joint space trajectory planning is we cannot ensure that the planned trajectory
is collision free and the behavior of the end.
The vector is predictable because we control actuators, but we don't know what's happening with the
motion of the end effector in the task space.
This is not the case in past space trajectory planning because we directly see that what is our trajectory
in task space?
That's all about introduction to trajectory planning.
See you on the next lesson.