Robot design

• The GRIP type acts as the interface between a person's hand and an object when performing actions like lifting, pushing, or pulling.
• The type of grip impacts the force generated on an object.
• The type of grip impacts the risk of injury.

Hand grips

• Grasps are divided into power grip and precision grip.
• Power grip involves forcefully holding an object and moving it with proximal muscles.
• Precision grip is when an object is manipulated with fingers.
• Cylindrical grip involves flexing fingers around an object, with the thumb on one side and fingers on the other, similar to holding a hammer.
• Spherical grip involves having fingers and thumb together around an object, similar to grabbing an apple or doorknob.
• Hook grip involves flexing the second through fifth fingers around an object in a hook-like manner, with the thumb extended and uninvolved. This grip requires thumb or median nerve ability.
• Pad to pad grip is when the thumb and one finger grip something
• Pinch grip is the thumb and one finger gripping.
• Three jaw chuck is the thumb and three fingers holding a pencil.
• Tip to tip grip is the use of the tip of the thumb against the tip of a finger, like picking up a coin, and it can be difficult with long fingernails.
• Lumbrical grip or plate grip has the MCP and PIP joint flexed and the DIP extended; the thumb opposes, and the grip is used for holding something horizontal, like a plate; lumbricals flex the MCP joint.

Medical robot design

• A medical robot is a complex system that includes an articulated and motorized mechanical structure
• A medical robot is a human-machine interface (HMI)
• Instruments, electronic components, and a software controller are parts of a medical robot.
• The elements of a medical robot are integrated to achieve daily medical tasks in optimal safety.
• Medical robot procedures are performed in a constrained environment with limited workspace, in collaboration with medical staff.
• One of the primary design steps is characterizing the gesture of the practitioner to determine system specifications in terms of workspace, velocity, effort, or precision. The robot's design and technology choices depend on this step.
• Dermarob is used in reconstructive surgery for skin harvesting and is equipped with a dermatome, an electric motor to vibrate the blades and perform skin incision.
• The instrument used involved a force sensor (ATI gamma force sensor 130 N / 10 Nm, 6 components) and a cable actuated velocity sensor (ASM Sensor).

Kinematic Choices

• Types of kinematic choices include conventional serial kinematics manipulator arms, parallel architecture manipulator arms, hybrid architecture, and architecture with remote center of motion.
• There are usually two kinds of joints one would use in a robot: Revolute (rotational) and prismatic (translational)
• A cylinder usually represents revolute joints.
• A cube or prism usually represents a prismatic joint.
• The industrial world almost only uses serial kinematic robots, which are non-redundant.
• Two architectures of serial kinematic robots can be identified: "anthropomorphic" and "SCARA" robots.
• Anthropomorphic robots are common in the automobile industry (welding, are painting) and made of a "carrier" and a "wrist", and typically have three degrees of freedom each.
• SCARA robots are used in manipulation industries (pick and place objects) and have two pivot joints and a prismatic joint, enabling a point to be placed in space, with a third pivot to guide the tool around a single axis and have 4 degrees of freedom total.
• Anthropomorphic robots workspaces have a spherical form and SCARA robots have cylinder shape
• SCARA robots are often well suited to a patient lying down.
• The first three joints of SCARA robot are not affected by gravity.
• SCARA robots are more predictable because the movement is constrained in a plane
• SCARA robot kinematic models are simpler
• Caspar, Hippocrates, and pathfinder are examples of anthropomorphic robots.
• ROBODOC, Dermarob, and PADvc are examples of Scara robots.
• Parallel architecture have several kinematic chains linking base to end-effector, unlike serial robots that consist of one.
• The most popular parallel robots are the hexapod that is used in motion simulators (motion platforms) and the delta robot used for rapid pick and place
• Parallel robots have a good "payload to robot weight" ratio and are designed to reach high velocities and accelerations, providing good mechanical stiffness and greater resolution.
• Their models are often easy to write as high-order polynomials, but difficult to resolve.
• Their calibration can be tricky and involve a lot of parameters.
• Parallel robots involve a less favorable ratio between footprint and workspace, which results in a significant bulk over the operative area.
• SurgiScope has "Delta" kinematics for translations with a conventional wrist for rotations.
• Spine Assist is a "hexapod"-like robot with 6 dof used in spinal surgery to perform pedicular screw placement with high accuracy.

Hybrid architecture

• Hybrid architectures include several kinematic chains in parallel, those chains can have serial kinematics integrating several actuators.
• It allows for solutions that offer good stiffness, an interesting workspace, and good orientation of the tools.
• CT-BOT robot to perform biopsies under a CT scanner is an example
• Remote center of motion is included as a feature of the design of multiple robots
• Linear-annular joint induces two constraints when the RCM is imposed by the environment.
• The Zeus robot architecture uses a trocar, two passive pivot joints forming a universal joint, and the instrument orientation controlled by the contact forces with the trocar.
• The apparent simplicity of these mechanisms has a price: it is essential to match the RCM of the mechanism with the insertion point ("fixed" to the patient) around which the movement should be performed, which leads to bulky adjustment devices and tedious registration procedures.

Concept selection

• The selection of actuators type and size impacts development of medical systems.
• Electric actuators are widely used on large holders
• Some robots use pneumatic actuators.
• The BirthSim robot uses a double acting linear pneumatic cylinder to simulate the pushes of a baby during labor.
• Bellows actuators move colonoscopes and perform movements in axial, angular and lateral directions.
• A McKibben actuator has a rubber tube covered with synthetic fiber is sealed off at one end and has a tube to supply air pressure at the other. The rubber tube is contracted by wrinkling, resulting in contraction force to the actuator's axis.
• McKibben artificial muscles mechanical operation is similar to physiological muscles.
• They have high power density and are light weight, ideal for integrating into robots with weight minimization, e.g. the tele-echography robot TER.
• Ultrasonic motors are compatible with the environment of a CT scanner and are used in interventional radiology.
• Ultrasonic motor (USM) converts ultrasonic vibrations into linear or rotary motion.

Technical Choices

• Sensors examples are miniature force sensors, vision systems, intra-cavity ultrasound probes.
• Electromechanical safety is ensured by high reduction ratios to limit the actuators' velocity, mechanical fuses, mechanical limitation of workspace (joint stops), limitation of joint torques, and fail-safe brakes.
• Electromechanical safety is ensured by duplication of measurement of the joint position.
• Redundancy ensures a fail-safe break is built in.
• Electromechanical safety is ensured by optimization of kinematics, rejection of singularities, quick tool change device, sterilizability, and mechanical reversibility.
• Electrical safety features include a "dead man" switch (DMS) and an emergency stop button.
• "Watchdog" boards monitor activity, ensure emergency stop buttons are in place, have separated electric circuits, ensure compliance with regulations, and limit current or voltage.
• Software safety features include online modification of workspace, verification of the consistency of redundant information, verification of the consistency between the set point and the current position increment, monitoring of the current's loop, robust processing of images and forces, advanced sensory-based control schemes, graceful shutdown in case of emergency, and reversibility via robot software.
• Software safety includes incremental design and implementation of software engineering techniques and avoidance of nondeterministic modules and HMI with unambiguous error messages.